US3916269A - Charging device - Google Patents

Charging device Download PDF

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Publication number
US3916269A
US3916269A US439166A US43916674A US3916269A US 3916269 A US3916269 A US 3916269A US 439166 A US439166 A US 439166A US 43916674 A US43916674 A US 43916674A US 3916269 A US3916269 A US 3916269A
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United States
Prior art keywords
electrode
corona
charging device
wires
distance
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Expired - Lifetime
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US439166A
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English (en)
Inventor
Willi Lanker
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Turlabor AG
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Turlabor AG
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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 The disclosure describes a charging device including 30 Foreign Application p i i Data an areal first electrode, a second electrode extending Feb 9 1973 Switzerland 001938/73 over a given area which is a corona electrode and has several individual electrodes and a source of voltage [52] U 8 Cl 317/262 A associated with the two electrodes.
  • the charging de- [Sl] llit CL H 19/00 ice has field-correction means in order to adapt the 58 Field of Search 317/262 A; .breakdcwndwliages of the 'Y eltfctmdes P 250/324 326 jacent con uctive parts not ymg at t e potentia o the corona electrode, 1n order to obtain both a um- [56] References Cited form, high charge-current density as well as a high total charge current. The combination of both a uni- UNITED STATES PATENTS form, high-charge, current density and a high total 3,l63,753 l2/1964 Dl Sabato et al.
  • 317/262 A Charge current provided the charge device permits 3,303,401 2/1967 Nauman 250/324 a substantial shortening of the time of the charging 3,611,074 10/1971 Weichardt 317/262 A process 3,656,021 4/1972 Furuichi et a].
  • 3l7/262 A 3,800,153 3/1974 Matsumoto et al 250/325 13 Claims, 10 Drawing Figures v, 11 12 I Iii l 14 15? is I d b I k" 7 21 k /6b 22 l l 1 1 I l l I I I I i I 1 I l l 1 ID I! I "I "I I I II I n I 91 PI PI? 15 1M?” I ,Q W W W W W W 41/ U.S. Patent Oct.28,1975 Sheet10f6 3,916,269
  • the present invention relates to a charging device.
  • the invention refers in particular to a charging device for the electrostatic charging of a charge carrier of an apparatus for the electrographic or electrophotographic production of images.
  • a charge carrier for instance a sheet of paper, bearing a known ZnO-containing coating
  • a voltage for instance, a few hundred volts and then by selective exposure producing an electrostatic charge image which depends on an original.
  • the duration of the operating cycle of such an apparatus for the production of images and thus its operating speed depends also on the period of time which is required for the charging of a given area, for instance a sheet of size A4, to a given voltage.
  • the performance properties of the charging device operating, for instance, as a corona device must be considerably increased. There has been no lack of attempts to achieve this purpose but no essential improvement could be obtained up to now. The most obvious idea of simply increasing the voltage at the corona electrode could not heretofore be carried out in practice since voltage breakdowns occurredto adjacent conductive parts which are not at the potential of the corona electrode.
  • the object of the present invention is therefore to create a charging device which permits a substantial shortening of the time of the charging process, referred to a given area.
  • a high charge-current density i as well as a high total charge current I are required.
  • the method of achieving this purpose concerns on the one hand the dimensioning of the corona electrode and on the other hand the use of field-correction means at the corona electrode and in its vicinity.
  • the present invention relates to a charging device consisting of an areal first electrode developed to receive a charge carrier, a second electrode extending over a given area which is developed as a corona electrode and has several individual electrodes, and of a source of voltage associated with the two electrodes, the charging device being characterized by the fact that it has field-correction means in order to adapt the breakdown voltages of the said individual electrodes to adjacent conductive parts not lying at the potential of the corona electrode, to each other in order thereby to obtain both a uniform, high charge-current density i as well as a high total charge current I
  • the invention will be described by way of example below with reference to the accompanying drawing in which:
  • FIG. 1 is a schematic showing of a first charging device.
  • FIG. 2 shows the course of the current in an arrangement in accordance with FIG. 1.
  • FIG. 3 is a diagrammatic showing of a second charging device.
  • FIG. 4 shows the course of the current of an arrangement in accordance with FIG. 3.
  • FIG. 5 is a perspective view of one embodiment of the present invention.
  • FIG. 6 is a diagram of the charging device of FIG. 5.
  • FIG. 7 shows the course of the current in an arrangement in accordance with FIGS. 5 and 6 respectively.
  • FIG. 8 is a diagram of a charging device with corona wires arranged in pairs.
  • FIG. 9 is a diagram of a charging device with conductive lid.
  • FIG. 10 is a diagram of a charging device with control electrode.
  • corona voltage which is as high as possible.
  • the corona voltage is limited by the breakdown voltage at which the maximum current density is given off.
  • the operating voltage of the corona electrode must now be selected sufficiently below its breakdown voltage.
  • the breakdown voltage is not a constant value for a given corona arrangement, but is rather dependent on various parameters, for instance the air pressure, the humidity of the air, etc.
  • the actual oper ating voltage U of a corona system must therefore be selected, for instance, 10% lower than the breakdown voltage U under normal conditions.
  • FIG. 1 shows a diagram of a first corona system K and the area F to be charged. I-Iere three corona wires D,, D and D arranged at a relatively large distance apart k are provided.
  • FIG. 2 shows the variation of the current which can be obtained with a system in accordance with FIG. 1. It should be noted that as a result of the relatively large spacing k, a charge-current density i which lies approximately at the value i "m is present only in the immediate vicinity of the individual corona wires D D and D while in the zones between the individual corona wires, only a relatively low charge-current density is obtained.
  • the areas f f f and f which are hatched in FIG. 2 are a measure of the deficit of charge-current density which occurs as a result of the selected arrangement of the corona wires.
  • FIG. 2 makes it now obvious to-select a corona arrangement in which the individual corona wires are arranged at a substantially smaller distance apart.
  • FIG. 3 shows another corona system in which 7 corona wires D D, are arranged over the length I, the distance between two consecutive corona wires being reduced as compared with the arrangement of FIG. 1 to the value k.
  • FIG. 4 again shows the variation of the current of the corona arrangement of FIG. 3.
  • the expectedresult namely a charge-current density which is as uniform as possible over the entire length is not obtained.
  • the high charge-current density i occurs only at the two outermost corona wires D and D',, while the other corona wires arranged between the two outermost corona wires produce only a very low charge-current density.
  • the deficit of charge-current density represented by thearea f f' and-f' could thus not be eliminated solely by the use of a larger number of corona wires and a smaller spacing between them.
  • the objct of the said fieldcorrection means is so to affect the course of the field in these regions that the breakdown voltage U, is as far as possible the same everywhere and at all parts of the corona electrode and thus all parts (wires) can be operated with the maximum charge-current density.
  • FIG. shows a perspective diagrammatic view of an embodiment of a charging device in accordance with the present invention.
  • a charging device can, for instance, be used in an electrostatic copier for the charging of a photoconductor which is thereupon exposed in accordance with an original copy in order to obtain a latent electrostatic charge image.
  • a latent electrostatic charge image can either be developed on the photoconductor itself in known manner or else it can be transferred to another support by the wellknown charge-transfer process.
  • Another possible use of such a charging device consists in electrostatically charging with it insulating layers, for instance individual sheets of paper, so that they will be held fast by the electrostatic forces then occurring on a transport device, for instance a Mylar conveyor belt, as a result of electrostatic forces of attraction.
  • FIG. 5 shows a portion from an apparatus having a charging device in accordance with the present invention.
  • Two rollers 2 and 3 rotatably supported in a chassis frame 1.
  • a carrier 5 for the receiving of an electroinstance be a highly insulating Mylar belt on the surface 6 of which an electric charge is to be applied.
  • a charging device 7 is provided for the application of this charge.
  • the charging device 7 has two lateral supporting walls 8 and 9, the supports 8a and8b and 9a and 9b respectively of which rest on the chassis frame 1.
  • the chassis frame 1 has been m'erely indicated in the drawing.
  • the supporting walls 8 and 9 consistof high-quality insulating material.
  • corona-resistant insulating material such as, for instance, polytetrafluorethlene or Plexiglas.
  • a thin wire having a diameter of, for instance, 0.1 mm is passed several times through a number of bore holes 10 in supporting-walls 8 and 9 between said walls 8 and 9. In this way there is obtained an arrangement of parallel wires 11'. 16 which are stretched at a uniform distance apart over the surface 6 of the carrier 5.
  • the end of the saidwire which emerges through the first opening 10 is connected with the conductor 17 of a high-voltage cable 18.
  • the high-voltage cable 18 leads to a pole ofa source of voltage (not shown) for the corona voltage U which is, for instance, 13 kv.
  • the other pole of the source of voltage is preferably connected with the chassis frame 1 or with ground.
  • rollers 2 and 3 are made of conductivematerial so that the bottom 6' of the carrier 5 assumes the potential of the chassis frame 1.
  • the bottom 6' of the carrier 5 can, for instance, be metallized at least in the region in which its surface is to be charged, thus forming a grounded electrode.
  • the continuous carrier 5 is charged'electro statically on its surface 6 by said charging device 7.
  • This insulating board consists preferably of a corona-resistant insulating material such' as polytetrafluorethylene.
  • This insulating board consists preferably of a corona-resistant insulating material such' as polytetrafluorethylene.
  • FIG. 6 shows schematically the construction of the charging device of FIG. 5, and FIG. 7 shows the course of the charge-current density i along the length l of the area to be charged which is obtained with this charging device. It can be-readily seen that the entire hatched area f f which represents the deficit of charge-current density is substantially less in FIG. 7 than it is in FIG. 4 which correponds to a charging device without field-correction means.
  • Such a fieldcorrected charging device has the result that the same field distribution and thus the same breakdown voltage U ,,.is present as far as possible'at all corona wires 1 1-16 and they can thus all be operated with the same maximum operating voltage and all give off the optimum charge-current density; while without field-correction, a disturbing marginal field occurs at the outermost corona wires.(FIGS.
  • the field-correcting .limiting elements 21, 22 can consist, for instance, of corona-resistant insulating boards, struts, bar grids or nettings which form essentially insulating surfaces which are charged by the corona electrode and therefore act to correct the field.
  • multi-wire corona'devices one can, for-instance, obtain an increase in the total charge current I, of two to five times, with corresponding reduction of the charging time, as compared with similar devices without field-correction means.
  • insulating sleeves 25 can be placed on the ends of the corona wires 1 l". 16 and on the parts of said wires extending along the outer sides of the supporting surfaces 8 and 9 as further fieldcorrection means. These insulating sleeves 25 also represent field-correction means.
  • FIG. 8 shows schematically the construction of a charging device with corona wires 11 16 arranged in pairs.
  • the first pair is formed by corona wires 1 1 and 12, the second pair by corona wires 13 and 14, and the third pair by corona wires 15 and 16.
  • the distance k between the two wires of a pair is less than the inside distance w between the adjacent wires of two pairs.
  • the distance b from the limiting element 21' and 22 is preferably approximately equal (and even larger in the case of conductive limiting elements) than the inside clearance w.
  • field-correction means can be used in this case also:
  • FIG. 9 shows schematically another advantageous embodiment of the charging device 7.
  • a conductive surface 27 which normally lies at ground potential.
  • I the total charge-current I as well as the portion of the current I, flowing to the lid are also entered.
  • Field-correction means can now see to it that I, becomes much smaller than I as a result of which the said swingings of the corona wires are suppressed.
  • this is obtained by making r larger than d, preferably r l'.5d.
  • FIG. 10 shows 'anotheradvantageous embodimentof the invention.
  • a control electrode 28 is arranged in the space between the corona electrode 11 l6 and the surface 6 to be charged.
  • the control electrode 28 consists, for instance, of a large number of parallel wires arranged close together and extending in a plane parallel to the corona electrode formed by the corona wires 11 16.
  • Another possibility for the correction of the edge field instead of using the limiting elements 21, 22 in FIG. 6, consists in making the two outermost wires (11, 16') of the corona electrode so thick (for instance 0.5 1 mm) that no corona discharge occurs there as shown in broken lines in FIG. 6.
  • a charging device comprising an areal first electrode adapted to support a charge carrier, a second electrode extending over a given area which is a corona electrode and has several individual corona electrode wires, a source of voltage associated with both electrodes, and field-correction means of insulating material arranged outside of the volume defined by the said area of said corona electrode and the areal first electrode, for adapting the breakdown voltages of the said individual corona electrode wires to adjacent conductive parts not lying at the potential of the corona electrode wires in order thereby to obtain both a uniform, high charge density i and a high total charge current 2.
  • said field-correction means is at least one insulating element arranged at an edge of the charging device.
  • the charging device according to claim 1, further having individual electrodes arranged as fieldcorrection means at the edge of the corona electrode which have a greater thickness than the. individual electrodes arranged inward thereof.
  • said field-correction means comprises an insulating surface 'arr'anged'on the side of the corona electrode facing away from the first electrode.
  • a conductive surface is arranged on the side of the corona electrode facing away from the first electrode at a distance (r) from the corona electrode, and the distance (r) is at least 1.5 times as great as the distance (d) of the corona electrode from the first electrode opposite it which does not lie at the potential of the corona electrode.
  • a third electrode acting as a control electrode is arranged between the first electrode and the second electrode.
  • control electrode comprises one wire per corona electrode wire, which wires are parallel to each other.
  • control electrode is arranged at a distance (a) from the second electrode which is only slightly less than the distance (d') between the secondelectrode and the charge carrier.

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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)
US439166A 1973-02-09 1974-02-04 Charging device Expired - Lifetime US3916269A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH193873A CH548627A (de) 1973-02-09 1973-02-09 Elektrostatische aufladevorrichtung.

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US3916269A true US3916269A (en) 1975-10-28

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US439166A Expired - Lifetime US3916269A (en) 1973-02-09 1974-02-04 Charging device

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US (1) US3916269A (enrdf_load_stackoverflow)
CA (1) CA1023792A (enrdf_load_stackoverflow)
CH (1) CH548627A (enrdf_load_stackoverflow)
FR (1) FR2217736B1 (enrdf_load_stackoverflow)
GB (1) GB1463712A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5715131A (en) * 1994-10-19 1998-02-03 Sharp Kabushiki Kaisha Charging device that can charge a body uniformly

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3163753A (en) * 1961-09-12 1964-12-29 Du Pont Process and apparatus for electrostatically applying separating and forwarding forces to a moving stream of discrete elements of dielectric material
US3303401A (en) * 1962-07-20 1967-02-07 Azoplate Corp Method and apparatus for imparting an electrostatic charge to a layer of insulating material
US3611074A (en) * 1969-11-24 1971-10-05 Ibm Corona discharge device
US3656021A (en) * 1970-01-29 1972-04-11 Katsuragawa Denki Kk Corona discharge device
US3800153A (en) * 1972-12-29 1974-03-26 Xerox Corp Electrophotography charging device
US3811048A (en) * 1972-09-12 1974-05-14 Xerox Corp Electrophotographic charging apparatus

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3163753A (en) * 1961-09-12 1964-12-29 Du Pont Process and apparatus for electrostatically applying separating and forwarding forces to a moving stream of discrete elements of dielectric material
US3303401A (en) * 1962-07-20 1967-02-07 Azoplate Corp Method and apparatus for imparting an electrostatic charge to a layer of insulating material
US3611074A (en) * 1969-11-24 1971-10-05 Ibm Corona discharge device
US3656021A (en) * 1970-01-29 1972-04-11 Katsuragawa Denki Kk Corona discharge device
US3811048A (en) * 1972-09-12 1974-05-14 Xerox Corp Electrophotographic charging apparatus
US3800153A (en) * 1972-12-29 1974-03-26 Xerox Corp Electrophotography charging device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5715131A (en) * 1994-10-19 1998-02-03 Sharp Kabushiki Kaisha Charging device that can charge a body uniformly

Also Published As

Publication number Publication date
DE2402904B2 (de) 1976-04-15
FR2217736A1 (enrdf_load_stackoverflow) 1974-09-06
DE2402904A1 (de) 1974-08-29
FR2217736B1 (enrdf_load_stackoverflow) 1976-06-25
CA1023792A (en) 1978-01-03
CH548627A (de) 1974-04-30
GB1463712A (en) 1977-02-09

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