US3770972A - Corona charger configuration - Google Patents

Corona charger configuration Download PDF

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Publication number
US3770972A
US3770972A US00287694A US3770972DA US3770972A US 3770972 A US3770972 A US 3770972A US 00287694 A US00287694 A US 00287694A US 3770972D A US3770972D A US 3770972DA US 3770972 A US3770972 A US 3770972A
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United States
Prior art keywords
wires
charging
corona
field
original
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Expired - Lifetime
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US00287694A
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English (en)
Inventor
P Hastwell
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Savin Business Machines Corp
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Savin Business Machines Corp
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/02—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices
    • G03G15/0291—Apparatus for electrographic processes using a charge pattern for laying down a uniform charge, e.g. for sensitising; Corona discharge devices corona discharge devices, e.g. wires, pointed electrodes, means for cleaning the corona discharge device

Definitions

  • ABSTRACT Charging Apparatus for an electrostatic copier wherein a photoconductive surface is electrostatically charged and exposed to a light pattern forming a latent image thereon which is developed by application ofa suitable toner.
  • the photoconductive surface is charged by exposure to a corona discharge field which is shielded in a manner to provide uniform charge distribution over the major area of the surface, and shaped so as to modify charge near the borders of the surface in a manner which compensates for variations in the intensity of the light pattern projected thereon.
  • PAIENIEDRM s 1915 SHEET 2 BF 3 CORONA CHARGER CONFIGURATION BACKGROUND OF THE INVENTION In theart of electrostatic copying, an electrostatic charge is applied to a photoconductive surface. When the surface is exposed to a pattern of light a latent image is formed thereon which is developed by application of a toner material.
  • My system comprises means for shielding a grid of corona discharge wires to provide a more uniform charge pattern in the central portion of the copy surface and means for shaping or limiting the charge distribution near the borders of the surface.
  • One object of my invention is to provide an improved charging apparatus for an electrostatic copying machine which produces consistent copies of good clarity and high contrast, free of imperfections.
  • Another object of my invention is to provide an apparatus which applies a uniform electrostatic charge to central regions of a photoconductive surface and a compensating electrostatic charge at edges and corners of the surface.
  • a further object of my invention is to provide an electrostatic charger which emits a saturating level of charge, but in which a portion of the charge is shielded and blocked before reaching the photoconductive layer to shape the charge reaching the layer.
  • FIG. I is a schematic view of an electrostatic copying machine employing my invention.
  • FIG. 2 is a perspective view of the electrostatic char ger of FIG. 1 inverted from the position of FIG. I to reveal the charge shaping template.
  • FIG. 3 is a bottom plan view of the electrostatic charger of FIG. 1.
  • FIG. 4 is a sectional view of my electrostatic charger taken along the line 4-4 of FIG. 3.
  • FIG. 1 I have shown one form of electrostatic copying machine 10 using the invention.
  • Machine 10 has a generally rectangular opaque housing 12 whose upper surface carries an exposure window 14 on which the original 15 to be copied is placed.
  • An opaque cover sheet 16 of rigid or flexible design is hinged adjacent one edge of the exposure window to normally cover the original during transmission of the image contained thereon to the copy surface.
  • I provide an optical scanning system 20 comprising a pair of horizontally disposed parallel slide rails fixed below the exposure window 14.
  • the rails 22 support a carriage 30 for linear travel thereon.
  • An endless drive chain 26 carried by sprockets 28 is connected to the carriage 30 and is driven by a motor (not shown) to reciprocate the carriage 30 between the limits of the rails 22.
  • the carriage 30 houses an optical system which exposes the photoconductive surface to a light pattern derived from the original.
  • the optical'system comprising a set of mirrors 34, a lamp 32, a reflective lens system 36 and a shutter 38, is activated, and the system sweeps across the face of the original, transmitting to the photoconductive surface a reflected light pattern derived from the original.
  • a shaft 40 carries a roll 42 of coated paper or other flexible sheet material 44 to which the image of the original is to be transferred.
  • Material 44 may comprise a conductive base layer which is coated with a suitable photoconductive material, such as finely divided zinc oxide particles in an insulating resin binder.
  • the roll 42 is mounted on the shaft 40 in such. a manner that when a length of the material 44 or copy paper" is drawn therefrom the photoconductive face of the copy paper is in appropriate orientation for exposure to light from the original.
  • a copying operation is initiated on energization of a solenoid 46 which causes a pair of feed rollers 48 to drawthe copy paper 44 from the roll 42 around guide rollers 50.
  • the feed rollers 48 advance the copy paper 44 past a cutting station, indicated generally by reference numeral 52, comprising rotary cutter 53 and stationary blade 51, to a pair of forwarding rollers 54 which continue to transport the copy paper past a corona charging system, indicated generally by reference numeral 56 to a conveyor belt assembly indicated generally by reference numeral 58.
  • the corona charging system 56 comprises a charger housing 60 in which a plurality of horizontally disposed parallel corona charging wires oriented normally to the direction of motion of the copy paper 44 is mounted.
  • the corona wires 130 are arranged to line in a plane generally parallel to a horizontally disposed,
  • I provide a rotary solenoid which is energized following the charging step to rotate the rotary cutter 53 through a small angle, and into contact with the stationary blade 51 to shear the copy paper 44 to a preselected length.
  • the conveyor assembly comprises a plurality of horizontally disposed parallel belts 68 arranged to pass over drive roller 72 and idler roller 70.
  • the belts 68 are driven by a motor (not shown) through a gear chain (not shown) tracking a pinion 74 securely mounted on the drive roller 72.
  • Air is drawn downward through a multiplicity of small holes in an exposure bed 76 by the action of a partial vacuum created by a motor driven fan 78.
  • the charged photoconductive surface remains stationary on the exposure bed 76 during exposure by optical scanning system 20.
  • the conveyor assembly 58 transports the image bearing surface to a developing station indicated generally by reference numeral 86 comprising a paper guide arm 88, a developer trough 90 and squeegee rollers 92 which deliver the developed copy to a discharge slot 94.
  • a developing station indicated generally by reference numeral 86 comprising a paper guide arm 88, a developer trough 90 and squeegee rollers 92 which deliver the developed copy to a discharge slot 94.
  • I may arrange in trough 90 a set of rollers (not shown) or a similar instrumentality for applying to the exposed photoconductive surface the toner material contained in the trough.
  • I provide automatic controls (not shown) to execute a programmed sequence of steps comprising drawing copy material 44 from roll 42, charging the photoconductive surface of the paper, cutting the copy paper to a desired length, exposing the charged surface to a light pattern derived from the original, developing the image bearing surface and discharging the developed copy.
  • I further provide a density control knob 96, calibrated for light densities ranging from dark to light which controls the voltage applied to the corona charging wires 130.
  • My charger housing 60 and conductive support plate 62 are arranged relative to one another so that the corona wires 130 and the photoconductive surface of the copy paper lie in parallel planes. Forwarding rollers 54 transport the photoconductive surface at constant speed relative to the corona wires, in a direction of motion normal to their orientation.
  • a form of my electrostatic charging system comprises a rectangular housing 60 with a shielding base plate 104, approximately 9 inches X 3 inches suitably joined to enclosing side walls 106 approximately 3 inches X 1 inch and closing end walls 108 approximately 9 inches X 1 inch.
  • the bottom of the charger is open when the charger is in the position indicated in FIG. 1.
  • Blocks and 112 may be fabricated of one of several insulating materials. I have found the acrylic resin of the type known as plexiglas, which is the registered trademark of Rohm and Haas Co., to be suitable.
  • a brass bus bar 116 embedded in block 110 extends transversely from a cable socket 117, in one wall of the block 110, to a series of internal connections 111 to horizontally disposed parallel brass rods 119 oriented normally to the direction of bus bar 116 and extending outwardly from the block 110 into the channels 113.
  • several horizontally disposed parallel insulating rods 120 are affixed within block 112 and extend into channels toward block 110.
  • the corresponding pairs of brass rods 119 and insulating rods lie along parallel, colinear line segments in a common plane above and parallel to the base plate 104.
  • each of the tension springs 122 is connected to and serves to hold an end ofa tungsten corona wire 130.
  • the three parallel corona wires 130 are held taut between corresponding sets of the springs 122.
  • Arrayed between the wires 130 are secured by notches in blocks 110 and 112 are several dividers 132.
  • the dividers are made of metal and grounded together with the walls 108 and 106 and base plate 104 of the charger housing.
  • corona current is created when a sufficiently high voltage is applied between the wires and the parallel conducting surface beneath the photoconductive material to be charged. Air near the wires becomes ionized and the ions are swept by the electric field toward the photoconductive surface.
  • the corona discharge threshold voltage for a corona wire is an increasing function of the diameter of the wire.
  • the corona on a negative wire appears as a bluish-white sheath over the surface of the wire connecting bright' glowing foci uniformly spaced along the wire.
  • the direction of motion of the photoconductive surface is normal to the orientation of the wires 130.
  • the charge distribution on the photoconductive surface would appear as a pattern of parallel bands of high charge density oriented in the direction of motion of the surface and corresponding to the spacing of the corona foci along the wires 130.
  • the metal dividers perform a valuable function in obtaining a uniform charge distribution.
  • the dividers attract much of the corona current generated so that the wires may be operated at a potential exceeding the threshold voltage without overcharging the photoconductor. Operation at voltages exceeding the threshold voltage reduces variations in corona current owing to variations in wire diameter or to adherence of contaminants to the wire.
  • the dividers also serve to spread the bands of charge so that they cover the photoconductive surface in a more uniform manner.
  • the height of the divider must be about one-sixteenth of an inch below the distance of the wires from the base plate 104. If the dividers extend above the wires the corona current is too severely diminished. If the dividers are too far below the wires, then not enough corona current is attracted and the photoconductor is unevenly charged as previously described.
  • FIGS. 2 and 3 illustrate the preferred elliptical opening for my charging apparatus. However, any one or more openings of any shape which by experimental determination achieve a desired diminution in charge intensity at any region of the photoconductive surface may be employed.
  • the wires are raised to corona potential by a voltage source connected to the wires through a cable 118.
  • My charger 56 is placed in the electrostatic copying machine so that the corona wires are 1 inch above the photoconductive surface as viewed in FIG. 1. This height was determined by the charge acceptance rate of the paper and the relative speed of traverse of the carriage.
  • I have provided an apparatus for uniformly charging the central region of a photoconductive surface and simultaneously shaping the distribution pattern so that less charge is deposited on border regions of the surface to compensate for the diminution in light intensity subsequently projected thereto.
  • an electrostatic copying machine having an exposure system for subjecting the surface of a photoconductor to an image of an original to be reproduced over a generally rectangular'illuminated area, the light intensity of which falls off at the edges and corners of said area and having means for positioning the photoconductive surface adjacent to a charging station
  • charging apparatus comprising means at said charging station for producing a generally rectangular corona discharge field pattern, and means for so modifying said field pattern adjacent to the periphery thereof as to'compensate for said fall off in light intensity over said illuminated area to cause said machine to produce a copy having contrast throughout corresponding to the contrast in the original.
  • said field producing means comprises a plurality of corona wires, means mounting said wires in spaced parallel relationship and respective grounded conductive plates disposed in the spaces between said wires.
  • charging apparatus comprising a plurality of corona wires adapted to be energized to produce a charging field, means mounting said wires in spaced relationship at said charging station with the lengths thereof extending across said path, field distributing plates disposed in the spaces between said wires, said plates having upper edges spaced slightly below said wires, a field shaping plate means having a generally centrally located opening therein for modifying said field adjacent to the periphery thereof so as to compensate for said fall off in light intensity to cause said machine to produce a copy having contrast throughout corresponding to the contrast of the original, and means mounting said plate between said wires and said path.
  • Apparatus as in claim 10 in which said opening is generally oval and in which the major axis thereof is the path.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Control Or Security For Electrophotography (AREA)
US00287694A 1972-09-11 1972-09-11 Corona charger configuration Expired - Lifetime US3770972A (en)

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US28769472A 1972-09-11 1972-09-11

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US3770972A true US3770972A (en) 1973-11-06

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US (1) US3770972A (fr)
JP (1) JPS4969146A (fr)
AU (1) AU5769173A (fr)
DE (1) DE2338488A1 (fr)
FR (1) FR2199139A1 (fr)
IT (1) IT992714B (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3875407A (en) * 1974-01-16 1975-04-01 Xerox Corp Corona generator cleaning apparatus
US3943418A (en) * 1974-03-08 1976-03-09 La Cellophane Corona charging device
US4104521A (en) * 1976-04-09 1978-08-01 Amp Incorporated Corotron connector
US20060176641A1 (en) * 2003-06-11 2006-08-10 Peter Gefter Ionizing electrode structure and apparatus
US7339778B1 (en) * 2003-06-11 2008-03-04 Ion Systems Corona discharge static neutralizing apparatus

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4377839A (en) * 1980-01-14 1983-03-22 Inter-Probe, Inc. Energy transfer apparatus
WO1993011472A1 (fr) * 1991-11-29 1993-06-10 Spectrum Sciences B.V. Appareil d'imagerie electrographique serielle

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2965756A (en) * 1959-10-09 1960-12-20 Haloid Xerox Inc Electrostatic charging apparatus
US2965481A (en) * 1955-08-01 1960-12-20 Haloid Xerox Inc Electrostatic charging and image formation
US3160746A (en) * 1961-05-01 1964-12-08 Xerox Corp Corona charging apparatus for non-uniformly charging a xerographic plate in a predetermined manner
US3321768A (en) * 1960-05-12 1967-05-23 Burroughs Corp Electrostatic recording with interchangeable stencils
US3578970A (en) * 1968-05-03 1971-05-18 Plastic Coating Corp Variable width corona discharge apparatus with means to shield or vary a predetermined length of a corona discharge wire
US3619609A (en) * 1968-11-25 1971-11-09 Katsuragawa Denki Kk Corona discharge device for electrophotography employing interleaved discharge electrode elements and counter electrode elements

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2965481A (en) * 1955-08-01 1960-12-20 Haloid Xerox Inc Electrostatic charging and image formation
US2965756A (en) * 1959-10-09 1960-12-20 Haloid Xerox Inc Electrostatic charging apparatus
US3321768A (en) * 1960-05-12 1967-05-23 Burroughs Corp Electrostatic recording with interchangeable stencils
US3160746A (en) * 1961-05-01 1964-12-08 Xerox Corp Corona charging apparatus for non-uniformly charging a xerographic plate in a predetermined manner
US3578970A (en) * 1968-05-03 1971-05-18 Plastic Coating Corp Variable width corona discharge apparatus with means to shield or vary a predetermined length of a corona discharge wire
US3619609A (en) * 1968-11-25 1971-11-09 Katsuragawa Denki Kk Corona discharge device for electrophotography employing interleaved discharge electrode elements and counter electrode elements

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3875407A (en) * 1974-01-16 1975-04-01 Xerox Corp Corona generator cleaning apparatus
US3943418A (en) * 1974-03-08 1976-03-09 La Cellophane Corona charging device
US4104521A (en) * 1976-04-09 1978-08-01 Amp Incorporated Corotron connector
US20060176641A1 (en) * 2003-06-11 2006-08-10 Peter Gefter Ionizing electrode structure and apparatus
US7339778B1 (en) * 2003-06-11 2008-03-04 Ion Systems Corona discharge static neutralizing apparatus
US7483255B2 (en) 2003-06-11 2009-01-27 Ion Systems Ionizing electrode structure and apparatus

Also Published As

Publication number Publication date
FR2199139A1 (fr) 1974-04-05
DE2338488A1 (de) 1974-03-28
AU5769173A (en) 1975-01-09
JPS4969146A (fr) 1974-07-04
IT992714B (it) 1975-09-30

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