US3816749A - Exposure controlled corona device - Google Patents

Exposure controlled corona device Download PDF

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Publication number
US3816749A
US3816749A US00306766A US30676672A US3816749A US 3816749 A US3816749 A US 3816749A US 00306766 A US00306766 A US 00306766A US 30676672 A US30676672 A US 30676672A US 3816749 A US3816749 A US 3816749A
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United States
Prior art keywords
shield
corona
electrode
corotron
photoconductive
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US00306766A
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English (en)
Inventor
A North
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Individual
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Individual
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Publication date
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Priority to US00306766A priority Critical patent/US3816749A/en
Priority to NL7312242A priority patent/NL7312242A/xx
Application granted granted Critical
Publication of US3816749A publication Critical patent/US3816749A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

  • the present invention relates to the field of xerography and in particular to an improved corona generating device for imposing electrostatic charge on a xerographic surface.
  • a photoconductive surface, or photoreceptor In xerography, one known method by which a photoconductive surface, or photoreceptor, is sensitized is by the use of ions generated in a corona discharge. To effect the corona discharge, one or more corona wires is maintained at a high potential andthe resultant electric field strength at the surface of the wire causes air molecules to become ionized. These ions are drawn to the xerographic plate by thedifference' in potential existing between wire and plate. The build-up of these ions on the plate creates a potential across the plate.
  • a grounded shield is used in association with the corona wire so as to control and direct its discharge onto the photoreceptor.
  • corona generating devices or corotrons as they have become known, is that the corona-emitting wire is maintainedat a high voltage. If it is desired to switch this voltage on and off, elaborate and expensive switching apparatus would be required to handle this high voltage.
  • Another object is to provide an optical means for switching a high voltage corona wire.
  • this invention is practiced in one form by a grounded corotron shield which is lined with a photoconductive insulator.
  • the photoconductive material becomes conductive and the shield is fully grounded.
  • the photoconductor is an insulator and the corona shield collects charge from the corona wire.
  • the shield becomes charged to a potential near that of the wire, the wire ceases to emit andthus the corotron is switched off.
  • FIG. 1 is a somewhat schematic representation of a corotron shield member, all disclosed and adjacent shield in operative position relative to a charge plate.
  • FIG. 2 is a fragmentary detail showing the structure of a corotron shield according to this invention.
  • FIG. I there is shown the general environment in which the present invention is used. It includes a corotron generally indicated at 2 disposed relative to a xerographic photoreceptor 4. As is well known, the corotron 2 acts to ionize the adjacent air and the resulting ions flow in a corona current to the corotron shield 6 and to the photoreceptor 4. Shield 6 is partly composed of a conductive material and is grounded. Photoreceptor 4 includes a conductive grounded plate 8 and a coating of photoconductive insulation 10. A corona wire 12 disposed within the shield 6 is maintained at a high voltage for the purpose of effecting the desired corona current.
  • a corona wire 12 disposed within the shield 6 is maintained at a high voltage for the purpose of effecting the desired corona current.
  • Shield 6 is composed of a transparent outer material 14 with a conductive layer 16 on its inner surface.
  • the conductive layer 16 is connected to ground.
  • a photoconductive layer 18 is in turn applied to the conductive layer 16.
  • a light source is schematically represented at 20 and positioned to illuminate the corotron shield 6.
  • the conductive layer 16 is either a transparent layer or semi-transparent, so as to permit illumination from source 20 to reach the photoconductive layer 18.
  • this corotron structure is as follows: When the shield is illuminated, the photoconductive layer 18 is conductive and the corotron shield 6 is therefore conductive and grounded in the usual manner. In the absence of light, the photoconductive layer 18 is an insulator so that charges emitting from the corotron wire 12 accumulate on the surface of layer 18. When the potential on the layer 18, that is to say on the inner surface of the corotron shield 6, reaches that of the corotron wire 12, the wire ceases to emit and the corotron is thereby switched off.
  • the intensity of light from source 20 determines the degree to which the photoconductive layer 18 is conductive (or insulative) and thus determines the degree to which the corotron emits. Additionally, the corotron and shield may be arranged so that the wire-to-shield spacing is less than the wire-to-plate spacing, permitting a greater measure of control by the shield over the corotron emission.
  • the corotron of this invention is controllable as to current output level.
  • This corotron shield obviates the necessity for expensive or intricate switching gear otherwise required for use with high voltages.
  • While the light. source 20 has been schematically represented on the side of the shield 6 opposite that of the corona wire 12, it may of course be located on the same side of the shield.
  • a corona generating device including a corona emission electrode and a shield electrode operatively disposed relative to said emission electrode, said shield electrode including an electrically conductive member which is connected to ground and a photoconductive insulative member electrically connected to said conductive member and disposed between said conductive member and said emission electrode, and
  • corona charge emitting from said emission electrode to said shield electrode flows to ground when said insulative layer is illuminated and accumulates on said shield when said insulative layer is not illuminated.

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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)
US00306766A 1972-11-15 1972-11-15 Exposure controlled corona device Expired - Lifetime US3816749A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US00306766A US3816749A (en) 1972-11-15 1972-11-15 Exposure controlled corona device
NL7312242A NL7312242A (enrdf_load_html_response) 1972-11-15 1973-09-04

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00306766A US3816749A (en) 1972-11-15 1972-11-15 Exposure controlled corona device

Publications (1)

Publication Number Publication Date
US3816749A true US3816749A (en) 1974-06-11

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ID=23186741

Family Applications (1)

Application Number Title Priority Date Filing Date
US00306766A Expired - Lifetime US3816749A (en) 1972-11-15 1972-11-15 Exposure controlled corona device

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US (1) US3816749A (enrdf_load_html_response)
NL (1) NL7312242A (enrdf_load_html_response)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4034221A (en) * 1975-04-07 1977-07-05 Ricoh Co., Ltd. Charging device for automatic copying apparatus

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2868989A (en) * 1956-01-03 1959-01-13 Haloid Xerox Inc Electrostatic charging method and device
US3220324A (en) * 1963-11-12 1965-11-30 Xerox Corp Photoconductively controlled corona charging
US3711710A (en) * 1969-11-07 1973-01-16 Australia Res Lab Method of and means for controlling corona emission

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2868989A (en) * 1956-01-03 1959-01-13 Haloid Xerox Inc Electrostatic charging method and device
US3220324A (en) * 1963-11-12 1965-11-30 Xerox Corp Photoconductively controlled corona charging
US3711710A (en) * 1969-11-07 1973-01-16 Australia Res Lab Method of and means for controlling corona emission

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4034221A (en) * 1975-04-07 1977-07-05 Ricoh Co., Ltd. Charging device for automatic copying apparatus

Also Published As

Publication number Publication date
NL7312242A (enrdf_load_html_response) 1973-11-26

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