US3598991A - Electrostatic charging device having a spark gap voltage regulator between a corona source and a voltage source - Google Patents

Electrostatic charging device having a spark gap voltage regulator between a corona source and a voltage source Download PDF

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Publication number
US3598991A
US3598991A US847865A US3598991DA US3598991A US 3598991 A US3598991 A US 3598991A US 847865 A US847865 A US 847865A US 3598991D A US3598991D A US 3598991DA US 3598991 A US3598991 A US 3598991A
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United States
Prior art keywords
potential
electrode
corona
source
charge
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Expired - Lifetime
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US847865A
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English (en)
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Louis N Nost
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Xerox Corp
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Xerox Corp
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05F—STATIC ELECTRICITY; NATURALLY-OCCURRING ELECTRICITY
    • H05F3/00—Carrying-off electrostatic charges
    • H05F3/04—Carrying-off electrostatic charges by means of spark gaps or other discharge devices
    • 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 A corona-charging device including a corona ZC, 250/49.5 GC wire surrounded by a grounded conductive shield.
  • the corona [51] Int. CIL 603g 15/00 wire is connected to either a positive or negative high-poten- [50] Field of Search ..250/49.560, tial source. Inserted in the circuit between the wire and the 49.561, 49.562 source is an airgap which draws an arc at high steroidsages.
  • the invention relates to a circuit for use with a corona discharge device which will produce more efficient and effective electrostatic chargingof a surface.
  • This novel circuit includes an air or spark gap device in the circuit connecting the corona electrode to the high-potentialsource.
  • a xerographic plate comprising a layer of photoconductive material on a conductive backing is given a uniform electric charge over its surface and then exposed to the subject matter to be reproduced by various projection techniques. This exposure discharges the plate in accordance with the light intensity reachingit, thereby creating a latent electrostatic image on or in the plate.
  • Developers which comprise, in general, a mixture of suitable pigmented or dyed resin base powder, hereinafter referred to as toner, and a granular carrier material which functions to generate triboelectric charges on, and to carry the toner. More specifically, the function of the carrier material is to provide mechanical control of the toner, or to carry the toner to an image surface and simultaneously provide almost complete homogeneity of charge polarity.
  • the toner powder is brought into surface contact with the photoconductive coating and is held thereon electrostatically in a pattern corresponding to the latent electrostatic image. Thereafter, the developed xerographic image may be transferred to a support material to which it may be fixed by any suitable means such as heat fusing.
  • This flow of ions is utilized to deposit an electrical charge on the grounded surface which is adjacent the opening in the conductive shield.
  • This type of charging apparatus is known in the art as a corotron.
  • the efficiency of this device depends on such factors as the diameter of the corona wire or coronode, the distance from the wire to the grounded plate and the geometrical characteristics of the charging corona.
  • the corona current flowing from the wire to the photoconductive plate is proportional to the potential difference between the two elements which changes during charging as a charge is built up on the insulated photoconductive surface.
  • the amount of the ion current between the wire and the plate controls the rate at which the photoconductive surface will charge. Also, if relativemovement occurs between the photoreceptor plate and corona charging device, as is conventional in xerography, the relative velocity therebetween will likewise control the charging rate of the photoreceptor.
  • Another object of this invention is to improve charging by a corona discharge device of photoconductive surfaces used in the art of xerography.
  • a further object of this invention is to increase the rate of charging of a photoconductive surface for a particular applied voltage.
  • Still another object of this invention is to improve the rapidity and uniformity at which a positive electrostatic charge is deposited upon a photoconductive surface.
  • a still further object of this invention is to improve the rapidity and uniformity at which a photoconductive surface is negatively charged.
  • a novel spark gap circuit for use with a corotron for charging with greater efficiency and economy in the xerographic process by increasing ion current flow for a given wire potential, as compared to prior art devices, and furthermore is operable at higher input potentials than heretofore possible.
  • connection of the corona wire to a positive electrical potential for providing a positive charge on the photoconductor plate will cause a corona to form in a sheath immediately around the corona wire.
  • the provision of an electrode spark gap or are in the circuit connecting the high voltage to the coronode will cause the corona emission to occur throughout substantially the entire area within the shield surrounding the wire.
  • Such a dispersed corona discharge has experimentally been found to improve charging of a plate at high potentials as compared to charging apparatus previously known,
  • the present invention increases the amount and rate of charging of a surface by allowing the corotron wire to be connected to greater maximum applied voltages than possible with prior charging apparatus.
  • the invention is also more efficient than conventional devices because it produces a greater charge on the plate for a given applied voltage.
  • Negative charging of a photoconductive surface is useful, for example, in reversal development, sometimes referred to as discharged area development, since the areas developed with toner are actually the areas of the image in which the charge has been dissipated. Such reversal development is useful in the xerographic process when negative microfilm is utilized to expose the photoreceptive surface.
  • the insertion of a spark gap in'the circuit between the high negative potential and the corona wire will disperse the corona beads along the surface of the'wire and form-a more substantially uniform corona discharge sheath around the wire. This will produce a more uniform negative charging of a plate than with conventional corotrons as well as producing greater charging at high potentials.
  • I is a schematic illustration of a suitable electrical mdlcanon of h amount of cilarging Produced y a corotron discharge appmms utilizing the invention f this li fi
  • the corona wire of a conventional corotron was connected to H 2 i a graphical illustration f the emciency f the various positive DC voltages up to maximum for the device pamms Show in HQ 1 as compared to a conventional 10 and the bare plate current was measured.
  • the maximum voltdevice; age that can be applied to a coronode is limited because of FIG.
  • FIG. 3 is a schematic illustration of a second embodiment of arcmg that will occur between the wire and grolfnded R a suitable corona discharge apparatus utilizing the invention
  • This Invention f f of this application 15 spark gap of inch inches and 0.035 inch inserted in a circuit DESCRWON OF THE PREFERRED EMBODIMENTS connecting the corona wire to the positive potential and these results are shown below in table 1.
  • a graphical representation Referring in particular to FIG. I, there is illustrated a of the comparative results of these tests is shown in FIG. 2.
  • corotron for depositing an electrostatic charge on a surface such as a photoconductive insulating material. Illustrated in the figure is a xerographic plate member 1 comprising a photoconductive insulating layer 2 on a grounded conductive substrate 3. A corotron unit 10 is positioned above the plate to deposit an electrical charge on the plate surface during relative movement therebetween.
  • the corotron unit includes a shield 11 which surrounds one or more coronodes or corona.
  • the shield 11 comprises an electrically conductive material and is preferably grounded.
  • a slit 13 is formed in the shield to allow ions to flow from the corona emission around the wire 12 to the photoconductive insulating surface 2 in order to deposit an electrical charge thereupon.
  • This slit 13 is preferably located directly between the corona wire and the photoconductive surface.
  • the corona discharge wire is connected by suitable means such as electrical circuit 14 to a high potential source HV-l.
  • the corona wire utilized in this embodiment is connected to the positive terminal of the high potential source HV-l, in order to place a positive charge on the plate I.
  • the circuit 14 includes a spark gap 15 inserted in the line.
  • the spark gap 15 comprises two adjacent electrodes 16 and 17 which cause an are or spark to be generated when a high potential is applied therebetween.
  • Any suitable electrodes can be utilized to generate such an arc, for example, an automobile spark plug.
  • the distance of the gap can also be made adjustable for increasing or decreasing various outputs according to the result desired.
  • An automobile spark plug is one example of an adjustable spark gap but other adjustable electrodes could be utilized.
  • FIG. 2 there is illustrated a graphic representation of the test results tabulated in table 1 as a plot of supply voltage to the coronode versus bare plate current. Comparing the curves for the conventional corotron and the two forms of the charging device according to the present invention. it is seen that greater plate current is formed by the conventional corotron at low voltages. However, above certain applied voltages the charge formed by the two forms of the corotron using an airgap according to this invention becomes significantly greater than the prior art device. This result indicates that the novel device disclosed herein will produce much greater efficiency at high voltage levels of operation.
  • the corotron utilizing the novel circuit of this application can operate at higher maximum potentials than prior art devices as well as produce more efficient charging at high voltages enabling, for example, xerographic drums to be more rapidly charged for faster operation.
  • FIG. 3 there is illustrated a second embodiment of the invention which places a negative charge on the photoconductive insulating layer or other surface.
  • This form of the invention is the same as the device shown in FIG. 1 except that the corona wire 12 is connected by a circuit including a spark gap 15 to a high negative potential I-IV-2.
  • This form of the invention produces similar results as demonstrated with reference to the device of FIG. 1 and produces more efficient charging than conventional corotrons. Further, as discussed earlier, the insertion of the spark gap in this form disperses the negative corona beads normally formed in negative potential corotrons and, therefore, it is possible to negatively charge a photoconductive insulating surface more uniformly than with the prior art devices.
  • corotron charging means also may encompass two or more corona wires or include shields of other shapes and forms. It is further within the scope of this invention to place a charge on surfaces other than a photoconductive insulating plate and to utilize the invention in any other application where it is desired to produce an electrostatic charge by corona emission.
  • the surface to be charged is not intended to be limited to a flat plate, but could be for example, a cylinder, web, or other form. Also, as is clear from the foregoing disclosure, the corotron of this invention could be mounted stationary with respect to a movable photoconductive surface.
  • a corona discharge device for depositing an electrostatic charge upon a surface comprising an electrode positioned adjacent to the surface to be charged, I a circuit means coupling a source of electrical potential to said electrode, and
  • spark gap means in series between said circuit means and said electrode for holding said electrode inactive below a predetermined potential, said predetermined potential being at least greater than the threshold potential at which said device emits corona, and to effect a continuous discharge of corona at a potential above said predetermined potential.
  • said electrode is an elongated wire positioned substantially parallel to said surface to be charged.
  • said source of electrical potential comprises a positive potential for depositing a positive charge upon said surface.
  • said source of electrical potential comprises a negative potential for depositing a negative charge upon said surface.
  • spark gap means is adjustable to vary the magnitude of the corona discharge potential and the charging rate of the device.
  • a corona discharge device of the type having an electrode for depositing an electrostatic charge upon a chargereceiving surface and a grounded electrode shield partially surrounding said electrode, said electrode and shield being operatively connected to circuit means for providing a source of electrical potential to the electrode, said discharge device further including spark gap means in series with said electrode and said shield for holding the corona discharge device inactive below a predetermined potential, said predetermined potential being at least greater than the threshold potential at which said device emits corona, and to effect a continuous discharge of corona at a potential above said predetermined potential whereby the surface is efficiently and uniformly charged.
  • corona discharge device of claim 9 wherein said spark gap means includes two electrodes positioned in spaced parallel relation to each other.

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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)
  • Elimination Of Static Electricity (AREA)
US847865A 1969-08-06 1969-08-06 Electrostatic charging device having a spark gap voltage regulator between a corona source and a voltage source Expired - Lifetime US3598991A (en)

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US84786569A 1969-08-06 1969-08-06

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US (1) US3598991A (es)
JP (1) JPS4820144B1 (es)
BE (1) BE754426A (es)
CH (1) CH513436A (es)
CS (1) CS163219B2 (es)
DE (1) DE2038742A1 (es)
ES (1) ES382404A1 (es)
FR (1) FR2056699A5 (es)
GB (1) GB1322378A (es)
NL (1) NL7011480A (es)
PL (1) PL70053B1 (es)
SE (1) SE359663B (es)
SU (1) SU442617A3 (es)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3794839A (en) * 1973-01-11 1974-02-26 Xerox Corp Corona generating apparatus
US4763141A (en) * 1987-08-03 1988-08-09 Xerox Corporation Printing apparatus with improved ion focus
US4841146A (en) * 1987-08-03 1989-06-20 Xerox Corporation Self-cleaning scorotron with focused ion beam
US5083145A (en) * 1990-06-27 1992-01-21 Xerox Corporation Non-arcing blade printer
US5587584A (en) * 1996-03-28 1996-12-24 Xerox Corporation Apparatus for charging a film on the internal surface of a drum
US5655186A (en) * 1996-03-28 1997-08-05 Xerox Corporation Light blocking ion charging apparatus
US5659176A (en) * 1996-03-28 1997-08-19 Xerox Corporation Scanning corotron
US5723863A (en) * 1996-03-28 1998-03-03 Xerox Corporation Ion charging apparatus with light blocking capability

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2221338A (en) * 1936-10-21 1940-11-12 Research Corp Deposition of material
US3084061A (en) * 1953-09-23 1963-04-02 Xerox Corp Method for formation of electro-static image
US3133193A (en) * 1962-01-22 1964-05-12 Du Pont Corona discharge apparatus for the surface treatment of plastic resins
US3370212A (en) * 1965-08-19 1968-02-20 Eastman Kodak Co Corona charging apparatus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2221338A (en) * 1936-10-21 1940-11-12 Research Corp Deposition of material
US3084061A (en) * 1953-09-23 1963-04-02 Xerox Corp Method for formation of electro-static image
US3133193A (en) * 1962-01-22 1964-05-12 Du Pont Corona discharge apparatus for the surface treatment of plastic resins
US3370212A (en) * 1965-08-19 1968-02-20 Eastman Kodak Co Corona charging apparatus

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3794839A (en) * 1973-01-11 1974-02-26 Xerox Corp Corona generating apparatus
US4763141A (en) * 1987-08-03 1988-08-09 Xerox Corporation Printing apparatus with improved ion focus
US4841146A (en) * 1987-08-03 1989-06-20 Xerox Corporation Self-cleaning scorotron with focused ion beam
US5083145A (en) * 1990-06-27 1992-01-21 Xerox Corporation Non-arcing blade printer
US5587584A (en) * 1996-03-28 1996-12-24 Xerox Corporation Apparatus for charging a film on the internal surface of a drum
US5655186A (en) * 1996-03-28 1997-08-05 Xerox Corporation Light blocking ion charging apparatus
US5659176A (en) * 1996-03-28 1997-08-19 Xerox Corporation Scanning corotron
US5723863A (en) * 1996-03-28 1998-03-03 Xerox Corporation Ion charging apparatus with light blocking capability

Also Published As

Publication number Publication date
ES382404A1 (es) 1973-04-16
NL7011480A (es) 1971-02-09
GB1322378A (en) 1973-07-04
BE754426A (fr) 1971-01-18
DE2038742A1 (de) 1971-02-18
PL70053B1 (es) 1974-02-28
SU442617A3 (ru) 1974-09-05
CS163219B2 (en) 1975-08-29
SE359663B (es) 1973-09-03
CH513436A (de) 1971-09-30
JPS4820144B1 (es) 1973-06-19
FR2056699A5 (es) 1971-05-14

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