US3909614A - Scorotron power supply circuit - Google Patents

Scorotron power supply circuit Download PDF

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Publication number
US3909614A
US3909614A US510336A US51033674A US3909614A US 3909614 A US3909614 A US 3909614A US 510336 A US510336 A US 510336A US 51033674 A US51033674 A US 51033674A US 3909614 A US3909614 A US 3909614A
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United States
Prior art keywords
current
shield
grid
corona
scorotron
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Expired - Lifetime
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US510336A
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English (en)
Inventor
Richard C Marshall
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Xerox Corp
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Xerox Corp
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Publication date
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Publication of US3909614A publication Critical patent/US3909614A/en
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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
    • G03G15/0266—Arrangements for controlling the amount of charge
    • 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

  • a scorotron for umformly charging an electrostatographic copying photoconductive surface has a coro [2]] Appl. No: 510,336 node wire, a conductive metal shield and a screen grid.
  • the coronode wire is supplied through a stabilizing resistor from an electrical inverter.
  • the screen and [30] Foreign Apphc auon pnonty Data the shield are connected together and commonly con- Umtcd Kmgdom 59538/73 nected to ground through two series connected resistors. From a connection point between the two resis- [52] US.
  • This invention relates to electrostatography. More particularly this invention relates to electrical circuitry for controlling acorona generating device applying electrostatic charge onto a suitable surface, such as a xerographic imaging plate.
  • the charging of the electrostatographic plate in preparationfor the exposure step can be accomplished by means of a corona generating device whereby electrostatic charge is applied to the electrostatographic plate to raise it to a potential of approximately 500 to 600 volts.
  • a corona generating device for this purpose is disclosed in the Walkup U.S. Pat. No. 2,777,957 wherein a plurality of parallel wires are connected in series to a high voltage source and are supported in a conductive shield that is arranged in closely spaced relation to the surface to be charged. When the wires are energized, corona is generated along the surface of the wires and ionsare caused to be deposited on the adjacent photoconductive surface.
  • Suitable means are usually provided to effect relative movement of the surface to be charged and the corona generating device.
  • a biased wire screen placed between the corona wires and the electrostatographic plate permits energizing the corona wires to a potential well above the corona threshold potential thereof without causing damage to the electrostatographic plate because the excess of corona current over that required for proper charging ofthe plate is drained offby' thebiased screen.
  • This type of corona generating device is referred to in the art as scorotron.
  • the corona threshold potential and the corona current from an energized wire are functions of the wire diameter, i.e., the corona threshold increases and the corona current for any given potential decreases as the wire diameter is increased. Variations inthe potential applied to corona wires ofa given diameter will cause relatively large changes in corona current with corresponding variations in the charging rate. In addition. the coronathresh'old potential and corona current are also affected directly by deposits of dust that may. accumulate on the wire and by variations of movement and ionized conditions of the air sheath surrounding the wire.
  • the contrast value, comparable to the contrast values obtained from silver halide papers, of the electrostatic latent image may be related directly to the potential charge on the electrostatographic plate before exposure, it is apparent that if the plate is not uniformly charged over its entire area, the contrast value of the electrostatic latent image obtained upon exposure will vary in different areas on the plate, and a mottled effect will be visible on the image when developed.
  • a prior art improved scorotron device whereby a uniform electrostatic charge can be deposited on the electrostatographic plate is disclosed in the Codichini U.S. Pat. No. 3,062,956.
  • the scorotron device described therein consists of a backup shield, corona generating electrode wires called the coronode, and screen wires.
  • the coronode wires by corona discharge, charging the photoconductive surface of the electrostatographic plate.
  • the potential applied to the plate surface is varied by changing the screen potential.
  • the charging circuit contains a current stabilizer and a regulated direct current power supply.
  • the current stabilizer is a device for controlling charging current by automatically adjusting the screen potential when a change is sensed in the current being supplied to the coronode.
  • any change in the charging current from the coronodes to the electrostatographic plate produces a change in the applied voltage to a control valve, for example, a high gain pentode, the output of said control valve being applied to the screen wires of the scorotron device.
  • a control valve for example, a high gain pentode
  • the output of said control valve being applied to the screen wires of the scorotron device.
  • any change in the charging current from the coronodes to the electrostatographic surface results in a change in the control valve resistance which, in turn, produces a change in the screen potential.
  • the resistance of the control valve increases thereby increasing the screen voltage to permit the charging current to increase back to its desired value and, of course, the converse is true as the charging current increases above a desired value.
  • the charging current can be maintained at a substantially constant value and is not adversely affected by any of the normal variables such as dirty wires, atmospheric changes, etc., which otherwise would affect the magnitude of the charging current.
  • scorotron power supply arrangement comprising an electrical, power supply means and circuit means arranged to sense the voltage at the grid and to supply control signals in de pendence thereon to adjust the power supply to alter the current supply to the coronode in a manner to maintain said voltage substantially constant.
  • the FIGURE here illustrates a scorotron supply arrangement according to the present invention, by way of example, in which a schematic circuit diagram of the arrangement is shown. 3
  • a scorotron has a coronode wire 11, and a conductive metal shield 12 directly electrically connected to a screen 13.
  • the coronode wire 11 is connected to be supplied through a stabilizing resistor 14 from a conventional inverter 15.
  • the screen 13 is connected through series connected resistors 16 and 17, to ground. From a point between the resistors 16 and 17 a feed-back loop is provided to supply signals to a conventional regulator 18 connected at the input side of the inverter 15.
  • the inverter is supplied from a transformer 19 through a rectifier bridge network 20.
  • a smoothing capacitor 21 is connected across the bridge network 20.
  • the current is supplied from the inverter output to the coronode wire 11 and corona discharge takes place as has been explained.
  • the grid voltage is required to be kept substantially constant at a predetermined value.
  • Theshield l2 and the screen 13 collect excess ions liberated at the surface of the coronode wire 11 to produce currents in the shield 12 and screen 13. The summation. of these currents,
  • biasing current flows through the resistors 16 and 17 to ground.
  • the biasing current in the described embodiment is maintained substantially constant, for maintaining the grid voltage substantially constant, by feeding, via the feed-back loop, a voltage signal generated by the biasing current to the regulator 18 to adjust the inverter output current to increase or decrease as the case may be. Whenever the voltage in the feed-back loop drops the output current is increased to raise thevoltage to its predetermined level. Similarly, if the voltage in the feed-back loop rises the output current is reduced by action of the regulator 18.
  • the surface to be charged charges up to a voltage substantially equal to the grid voltage provided that sufficient ions are liberated by the corona discharge.
  • the scorotron is capable of producing sufficient ions per unit time to charge up a moving surface, of a photoreceptor say, to becharged and that the power supply to the scorotron can supply sufficient current to cause release of those ions.
  • the present invention we control the charging of the surface to' be charged by maintaining the grid potential constant. This is acheived by altering the coronode current as and when required.
  • We monitor the grid voltage by measuring the current flowing through a resistor from the grid and made such adjustments automatically using the circuit means.
  • the g'rid current is found to be a substantially fixed ratio, duringnormal use of the coronode current so that by monitoring the grid voltage linearly, related adjustments of the coronode current are made.
  • the charging of the surface to be charged was controlled by altering the coronode current. This was achieved, however, by varying the grid potential, one such arrangement has already been mentioned above incorporating a pentode valve supply circuit.
  • the present invention provides scorotron supply arrangements which are comparatively insensitive to variations of surface speed, from either side of an optimum speed, of the surface to be charged.
  • the supply arrangements of the present invention can be provided using a small number of electrical components.
  • scorotron corona charging apparatus for charging a surface
  • said scorotron includes a conductive shield a conductive control grid and at least one corona emitting electrode
  • said improvement in said scorotron charging apparatus comprising:
  • adjustable electrical power supply means connected to said corona emitting electrode to provide a current supply thereto; sensing circuit means, including resistor means, for
  • sensing a voltage produced on said grid by said corona emitting electrode said sensing circuit means being connected to said power supply means to supply a control signal to said power supply means proportional to said voltage produced on said grid from said corona emitting electrode, said control signal from said sensing circuit means controlling said current supply from said power supply to said corona emitting electrode to main- .tain said voltage at said grid substantially constant, wherein said conductive control grid and said conductive shield are directly electrically connected together and to said resistor means of said sensing current means,
  • the copying apparatus of claim 1 further including regulator means connected to said resistor means, and inverter means connected between said regulator means and said corona emitting electrode.
  • a scorotron for uniformly charging an electrostatographic copying photoconductive surface comprising a corona emitting coronode wire, a conductive metal shield and a conductive screen grid, wherein the coronode wire is electrically supplied from a regulator,

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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)
US510336A 1973-12-21 1974-09-30 Scorotron power supply circuit Expired - Lifetime US3909614A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB5953873A GB1451647A (enrdf_load_stackoverflow) 1973-12-21 1973-12-21

Publications (1)

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US3909614A true US3909614A (en) 1975-09-30

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US510336A Expired - Lifetime US3909614A (en) 1973-12-21 1974-09-30 Scorotron power supply circuit

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US (1) US3909614A (enrdf_load_stackoverflow)
CA (1) CA1034640A (enrdf_load_stackoverflow)
GB (1) GB1451647A (enrdf_load_stackoverflow)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4077709A (en) * 1975-08-26 1978-03-07 Xerox Corporation Transfer charge control system
US4227233A (en) * 1976-10-01 1980-10-07 Olympus Optical Company Limited Corona discharge device for electrographic apparatus
US4456825A (en) * 1976-05-26 1984-06-26 Canon Kabushiki Kaisha Method of and device for charging by corona discharge
JPS6035760A (ja) * 1983-08-06 1985-02-23 Ricoh Co Ltd 感光体の帯電電位制御装置
JPS6055362A (ja) * 1983-09-07 1985-03-30 Ricoh Co Ltd 感光体の帯電電位制御装置
US4591713A (en) * 1984-01-03 1986-05-27 Xerox Corporation Efficient, self-limiting corona device for positive or negative charging
JPH03279973A (ja) * 1990-03-28 1991-12-11 Murata Mfg Co Ltd 帯電器用高圧電源回路
US5105330A (en) * 1989-05-26 1992-04-14 Brother Kogyo Kabushiki Kaisha Scorotron type charging apparatus
JPH0619625B2 (ja) 1984-04-02 1994-03-16 株式会社リコー 感光体の帯電電位制御装置
US5907155A (en) * 1998-01-08 1999-05-25 Xerox Corporation Constant DC offset coronode voltage tracking circuit
US20080290276A1 (en) * 2007-05-22 2008-11-27 Xerox Corporation Dicorotron having adjustable wire height
US20120069485A1 (en) * 2010-09-19 2012-03-22 Yefim Riskin Method and device for automatic positive and negative ion balance control in a bipolar ion generator
US9843169B2 (en) 2015-01-21 2017-12-12 Filt Air Ltd Bipolar ionizer with external ion imbalance indicator

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3068356A (en) * 1960-06-15 1962-12-11 Xerox Corp Xerographic charging apparatus
US3699388A (en) * 1967-07-06 1972-10-17 Ricoh Kk Apparatus for electrostatic charging of paper in electrophotographic reproduction
US3819942A (en) * 1973-05-07 1974-06-25 Savin Business Machines Corp Regulated power supply for corona charging unit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3068356A (en) * 1960-06-15 1962-12-11 Xerox Corp Xerographic charging apparatus
US3699388A (en) * 1967-07-06 1972-10-17 Ricoh Kk Apparatus for electrostatic charging of paper in electrophotographic reproduction
US3819942A (en) * 1973-05-07 1974-06-25 Savin Business Machines Corp Regulated power supply for corona charging unit

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4077709A (en) * 1975-08-26 1978-03-07 Xerox Corporation Transfer charge control system
US4456825A (en) * 1976-05-26 1984-06-26 Canon Kabushiki Kaisha Method of and device for charging by corona discharge
US4227233A (en) * 1976-10-01 1980-10-07 Olympus Optical Company Limited Corona discharge device for electrographic apparatus
JPS6035760A (ja) * 1983-08-06 1985-02-23 Ricoh Co Ltd 感光体の帯電電位制御装置
JPH0675222B2 (ja) 1983-08-06 1994-09-21 株式会社リコー 感光体の帯電電位制御装置
JPS6055362A (ja) * 1983-09-07 1985-03-30 Ricoh Co Ltd 感光体の帯電電位制御装置
JPH0673042B2 (ja) 1983-09-07 1994-09-14 株式会社リコー 感光体の帯電電位制御装置
US4591713A (en) * 1984-01-03 1986-05-27 Xerox Corporation Efficient, self-limiting corona device for positive or negative charging
JPH0619625B2 (ja) 1984-04-02 1994-03-16 株式会社リコー 感光体の帯電電位制御装置
US5105330A (en) * 1989-05-26 1992-04-14 Brother Kogyo Kabushiki Kaisha Scorotron type charging apparatus
JPH03279973A (ja) * 1990-03-28 1991-12-11 Murata Mfg Co Ltd 帯電器用高圧電源回路
US5907155A (en) * 1998-01-08 1999-05-25 Xerox Corporation Constant DC offset coronode voltage tracking circuit
US20080290276A1 (en) * 2007-05-22 2008-11-27 Xerox Corporation Dicorotron having adjustable wire height
US7763853B2 (en) * 2007-05-22 2010-07-27 Xerox Corporation Dicorotron having adjustable wire height
US20120069485A1 (en) * 2010-09-19 2012-03-22 Yefim Riskin Method and device for automatic positive and negative ion balance control in a bipolar ion generator
US8611065B2 (en) * 2010-09-19 2013-12-17 Yefim Riskin Method and device for automatic positive and negative ion balance control in a bipolar ion generator
US9843169B2 (en) 2015-01-21 2017-12-12 Filt Air Ltd Bipolar ionizer with external ion imbalance indicator

Also Published As

Publication number Publication date
CA1034640A (en) 1978-07-11
GB1451647A (enrdf_load_stackoverflow) 1976-10-06

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