US3716755A - Electrostatic charging and discharging apparatus - Google Patents

Electrostatic charging and discharging apparatus Download PDF

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Publication number
US3716755A
US3716755A US00212993A US3716755DA US3716755A US 3716755 A US3716755 A US 3716755A US 00212993 A US00212993 A US 00212993A US 3716755D A US3716755D A US 3716755DA US 3716755 A US3716755 A US 3716755A
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United States
Prior art keywords
charge
needles
electrostatic charging
insulator
absorbing electrode
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Expired - Lifetime
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US00212993A
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English (en)
Inventor
G Marx
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Kalle GmbH and Co KG
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Kalle GmbH and Co KG
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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
    • 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

Definitions

  • This invention relates to an apparatus for the electrostatic charging or discharging of the surface of web or sheet-like material, especially the electrostatic charging of photoconductive insulating layers, said apparatus including a charge-absorbing electrode in the form of a rotatable roller means with a roughened surface, said roller means being partially surrounded by an insulator and located between pointed corona electrodes in the form of a series of closely spaced needles which are externally protected by a second insulator, the outer extremity of the said roller means being spaced substantially equally to the points of the needles from the path of a material to be processed by the apparatus.
  • This invention concerns an apparatus for the electrostatic charging or discharging of the surface of web or sheet-like material.
  • Devices by means of which surfaces of materials with dielectric properties can be electrostatically charged or discharged are known. They usually consist of assemblies which emit discharge currents and comprise thin high-ten-- sion wires extending over the entire width of the web.
  • rotary roller electrodes For de-ionizing dielectric substances, rotary roller electrodes have been disclosed the surfaces of which are studded with discharge points and which cooperate with a smooth roller being the counterelectrode.
  • a disadvantage encountered with this equipment is the fact that the electrons emitted in the direction toward, the roller are easily misdirected due to deposit formation, so that some areas of the surface remain untreated.
  • Another charging electrode has been proposed in the shape of a roller consisting of a shaft on which a multitude of fixed metallic discs is provided which are arranged parallel with one another in' the axial direction of the shaft.
  • Increase of the corona high-tension is an expedient also used, but this requires an accurate variation of the distance between the point of discharge and the treated surface. This variation cannot be effected by an ordinary operator and requires the attention of an expert who, when changing the distance, also has to take into account the saturation limit of the material to be charged. An increase of the corona high-tension by itself is not feasible because it would cause breakdowns.
  • the present invention provides an apparatus for the electrostatic charging or discharging of the surface of web or sheet-like material, especially the electrostatic charging of photoconductive insulating layers, the apparatus including a charge-absorbing electrode in the form of a rotatable roller with a roughened surface, which roller is partially surrounded by an insulator and is located between pointed corona electrodes in the form of a series of closely spaced needles which are externally protected by a second insulator, the outer extremity of the roller being spaced substantially equally to the points of the needles from the path of a material to be processed by the apparatus.
  • This apparatus satisfies the most stringent requirements and ensures uniform charging or discharging across the entire surface with comparatively low corona voltages, irrespective of running speed and size of the processed surface and notwithstanding long periods of operation.
  • the apparatus preferably further includes a counterelectrode so arranged that the material can pass between it and the charge-absorbing electrode and adapted to be maintained at the same potential as the charge-absorbing electrode.
  • the effect achieved by the apparatus of the invention due to the particular arrangement of the needle points in conjunction With the roughened surface of the chargeabsorbing electrode, is that instead of the known coneshaped corona discharges emanating from every needle point, a dense uniform corona discharge is built up in which charge or discharge interruptions are avoided even if an occasional needle point fails to discharge. Furthermore, it has been found that this assembly ensures trouble-free working with a comparatively low corona tension, with constant distance from the processed material and over long periods of operation because the close spacing of the needles reduces the electrical stress on each needle point. A further result of this close spacing is that the unavoidable failure of an occasional needle is compensated by adjacent needles, so that charging or discharging takes place in a uniform manner. If desired the charge-absorbing electrodes also can be provided with a brush which removes the deposit upon it Without interrupting the working operation.
  • Substances Whose surfaces are to be charged or discharged may be paper, textiles, leather, rubber, plasticcoated metal foils or similar composite materials.
  • a preferred employment for the apparatus of the invention is the electrostatic charging of photoconductive insulating layers.
  • the apparatus of the invention can be used especially for charging the photoconductive insulating layers in re-enlargement apparatus.
  • FIG. 1 is an elevation of an apparatus of the invention including a counter-electrode
  • FIG. 2 is a similar view of a modified embodiment
  • FIG. 3 is a bottom plan view of the apparatus of FIG. 1.
  • a charge-absorbing electrode 1 is in the form of a solid rotatable roller consisting, for example, of chrome/nickel steel the surface of which is roughened, Roughening can be achieved by grinding, sandblasting, milling or some other form of mechanical treatment and produces a fine surface structure of partly edge-like and partly angular pointed character which aids the trapping or emitting of electrons.
  • rotation may be in the same direction as, or opposite to, the web movement.
  • rotation takes place in the same direction as web movement.
  • the two movements may be coupled or may ditfer from one another.
  • Corona electrodes 2 extend from a metal profile 9 to which individual, electrically conductive needles 3 are attached at the same level in parallel juxtaposition in comb-like fashion, as seen in FIG. 3.
  • the spacing of the needles or needle points 4 may amount to several needle diameters. More advantageously, the needles are spaced still more closely, however. In a preferred embodiment, the distance between the needles amounts to one needle diameter.
  • Needle diameters are from approximately 2 mm. to approximately 0.1 mm. Depending upon the material 10 to be charged or discharged, either thicker or thinner needles are used. Thus, when discharging textile surfaces, for example, thick needles will be used. In the case of electrostatically charging photoconductive insulating layers, for which employment the apparatus is particularly suitable, extremely thin needles having diameters of approximately 0. 1 to 1 mm. with very fine points are used. Needle diameters of 0.3 mm, have proved particularly successful.
  • the material used for the needles is steel, steel alloy or another metal alloy or a noble metal.
  • the charge-absorbing electrode 1 is situated in the center of the apparatus and is spaced apart from the material 10 to be processed by a perpendicular distance A which is mainly determined by the degree of high tension to be applied and amounts to between 5 and 30 mm.
  • the charge-absorbing electrode 1 is separated from the corona electrodes 2 by an insulator 5.
  • Two corona electrodes 2 are employed for one charge-absorbing electrode 1. It is also possible to arrange several assemblies consecutively, either on a straight or a curved path.
  • the points 4 of the corona electrodes 2 are equidistant from the charge-absorbing electrode roller 1 and extend parallel to the axis of the latter so that the outer extremity 7 (FIG. 2) of the charge-absorbing electrode 1 is approximately on a level with the needle points 4. Small level difierences are permissible, but care should be taken that the corona discharge takes place only from the needle points 4.
  • the direction of the needle arrangement of the corona electrode 2 with reference to the web plane 10 and the charge-absorbing electrode 1 can vary in such a way that the needles 3 extend either parallel to the plane of the web 10 and in a direction towards the charge-absorbing electrode 1 or at an angle to the normal to this plane.
  • the corona electrodes 2 are at an angle of 0 to about '60" to the Web plane, as shown in FIGS. 1 and 2. It would instead be possible to position the needle array perpendicular to the web plane and correspondingly to incline the needles in a direction away from the charge-absorbing electrode 1.
  • the selected angular arrangement also depends on whether a fiat construction or a rather more compact shape, for use in a larger machine, is to 'be employed.
  • the perpendicular distance B between the needle points 4 and the surface of the charge-absorbing electrode 1 depends upon the degree of high tension to be applied and amounts to about 5 to 15 mm. If the high tension is substantially increased, this distance may be larger. With a high tension of 10 kv. the distance is about. 10 mm.
  • the charge-absorbing electrode 1 may be provided with a cleaning device 12, for example in the shape of a fixed or rotary wiping brush which removes deposit adhering to the roller without interrupting the working operation.
  • the cleaning brush may be provided inside a recess of the insulator S.
  • the insulator 5 of the charge-absorbing electrode is of U-shaped cross-section, the width of the inner space depending upon the diameter of the charge-absorbing electrode.
  • the charge-absorbing electrode should be enclosed to such an extent that only a minor part of its surface projects beyond the limbs of the U.
  • the charge-absorbing electrode 1 projects only a few millimeters, e.g. l to 3 mm., beyond the insulation.
  • the U-limbs are preferably bevelled at their ends.
  • An insulator 6 outside the corona electrodes 2 shields these electrodes from external contact and may take the form of a housing.
  • the insulating material may consist of a suitable insulating substance of known type, especially a plastic material.
  • the insulator 5 may include ducts 11 for the admission of gases or the extraction of gases and/or dust particles.
  • ducts 11 for the admission of gases or the extraction of gases and/or dust particles.
  • a small degree of suction only is employed whereby the undesirable gases generated during charging or discharging are removed without, however, impairing the movement of the web or sheet. If stronger suction is required, a duplicate arrangement is advantageously used.
  • the introduction of air can improve web transport. When this method is applied, for example, an electrophotographic material becomes pressed against the counter-electrode 8 whereby contact is improved, the distance A is kept constant and steady web transport is achieved.
  • the position of the ducts 11 in the insulator 5 can be as desired.
  • the ducts 11 extend perpendicularly to the web 10 when suction is used and at an acute angle thereto and in the direction of web movement when air is introduced.
  • the counter-electrode 8 may be a cylinder or a metallic or metallized conveyor belt.
  • the apparatus of the invention may be equipped for high tensions in the region from 1 to 15 kv. or more.
  • high tensions of about 4 to about 12 kv. are suitable.
  • the apparatus is suitable for the charging or discharging of dielectric materials which travel at a speed of 1 to 50 rn./min., preferably 4 to 20 m./min.
  • An apparatus for the electrostatic charging or discharging of the surface of web or sheet-like material, especially the electrostatic charging of photoconductive insulating layers said apparatus including a charge-absorbing electrode in the form of a rotatable roller means with a roughened surface, said roller means being partially surroundedby an insulator and located between pointed corona electrodes in the form of a series of closely spaced needles which are externally protected by a second insulator, the outer extremity of the said roller means being spaced substantially equally to the points of the needles from the path of a material to be processed by the apparatus.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Physics & Mathematics (AREA)
  • Elimination Of Static Electricity (AREA)
US00212993A 1970-12-30 1971-12-28 Electrostatic charging and discharging apparatus Expired - Lifetime US3716755A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2064545A DE2064545C3 (de) 1970-12-30 1970-12-30 Vorrichtung zum elektrostatischen Auf- oder Entladen von Oberflächen eines Materials

Publications (1)

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US3716755A true US3716755A (en) 1973-02-13

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US00212993A Expired - Lifetime US3716755A (en) 1970-12-30 1971-12-28 Electrostatic charging and discharging apparatus

Country Status (15)

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US (1) US3716755A (es)
JP (1) JPS535816B1 (es)
AT (1) AT317678B (es)
AU (1) AU452831B2 (es)
BE (1) BE777424A (es)
CA (1) CA949122A (es)
CH (1) CH528199A (es)
DE (1) DE2064545C3 (es)
ES (1) ES398456A1 (es)
FR (1) FR2121128A5 (es)
GB (1) GB1377490A (es)
IT (1) IT945668B (es)
NL (1) NL7117483A (es)
SE (1) SE361748B (es)
ZA (1) ZA718702B (es)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3935517A (en) * 1975-01-02 1976-01-27 Xerox Corporation Constant current charging device
US4056372A (en) * 1971-12-29 1977-11-01 Nafco Giken, Ltd. Electrostatic precipitator
US4083073A (en) * 1976-03-31 1978-04-11 Leandro Bernardini Devices for neutralizing electrostatic charges and removing dust and particles from recording discs and the like
EP0060593A1 (en) * 1981-03-16 1982-09-22 Océ-Nederland B.V. Corona device
US4523082A (en) * 1983-05-05 1985-06-11 Sturdevant Eugene J Electrode shield device
US4579441A (en) * 1982-12-03 1986-04-01 Xerox Corporation Detacking apparatus
US4724508A (en) * 1985-12-18 1988-02-09 Becton, Dickinson And Company Method and apparatus for the continuous corona discharge treatment of the surface of formed articles
US5264989A (en) * 1991-06-14 1993-11-23 Bauer William S Apparatus for treating the surface of formed plastic articles using corona discharge
US5805407A (en) * 1995-09-07 1998-09-08 Fuji Photo Film Co., Ltd. Charge eliminating apparatus for a moving web
US6368675B1 (en) 2000-04-06 2002-04-09 3M Innovative Properties Company Electrostatically assisted coating method and apparatus with focused electrode field
US6475572B2 (en) 2000-04-06 2002-11-05 3M Innovative Properties Company Electrostatically assisted coating method with focused web-borne charges

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL7907492A (nl) * 1979-10-10 1981-04-14 Oce Nederland Bv Corona-inrichting.
DE3039951A1 (de) * 1980-10-23 1982-05-27 Andreas Dipl.-Ing. 6420 Lauterbach Ahlbrandt Vorrichtung zum behandeln der oberflaeche von gegenstaenden durch elektrische spruehentladung
JPS63167383A (ja) * 1986-12-22 1988-07-11 ゼロックス　コーポレーション コロナ帯電装置
DE19711342C2 (de) * 1997-03-18 1999-01-21 Eltex Elektrostatik Gmbh Aktive Entladeelektrode
DK177766B3 (da) * 2013-03-19 2018-04-30 Tresu As Enhed og fremgangsmåde til koronabehandling

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4056372A (en) * 1971-12-29 1977-11-01 Nafco Giken, Ltd. Electrostatic precipitator
US3935517A (en) * 1975-01-02 1976-01-27 Xerox Corporation Constant current charging device
US4083073A (en) * 1976-03-31 1978-04-11 Leandro Bernardini Devices for neutralizing electrostatic charges and removing dust and particles from recording discs and the like
EP0060593A1 (en) * 1981-03-16 1982-09-22 Océ-Nederland B.V. Corona device
US4579441A (en) * 1982-12-03 1986-04-01 Xerox Corporation Detacking apparatus
US4523082A (en) * 1983-05-05 1985-06-11 Sturdevant Eugene J Electrode shield device
US4724508A (en) * 1985-12-18 1988-02-09 Becton, Dickinson And Company Method and apparatus for the continuous corona discharge treatment of the surface of formed articles
US5264989A (en) * 1991-06-14 1993-11-23 Bauer William S Apparatus for treating the surface of formed plastic articles using corona discharge
US5805407A (en) * 1995-09-07 1998-09-08 Fuji Photo Film Co., Ltd. Charge eliminating apparatus for a moving web
US6368675B1 (en) 2000-04-06 2002-04-09 3M Innovative Properties Company Electrostatically assisted coating method and apparatus with focused electrode field
US6475572B2 (en) 2000-04-06 2002-11-05 3M Innovative Properties Company Electrostatically assisted coating method with focused web-borne charges
US6666918B2 (en) 2000-04-06 2003-12-23 3M Innovative Properties Company Electrostatically assisted coating apparatus with focused web charge field
US6716286B2 (en) 2000-04-06 2004-04-06 3M Innovative Properties Company Electrostatically assisted coating method and apparatus with focused electrode field

Also Published As

Publication number Publication date
GB1377490A (en) 1974-12-18
SE361748B (es) 1973-11-12
DE2064545B2 (de) 1979-09-06
CH528199A (de) 1972-09-15
DE2064545C3 (de) 1980-06-19
BE777424A (fr) 1972-06-28
FR2121128A5 (es) 1972-08-18
ES398456A1 (es) 1974-08-16
AU3704771A (en) 1973-06-21
AU452831B2 (en) 1974-09-12
AT317678B (de) 1974-09-10
ZA718702B (en) 1972-09-27
DE2064545A1 (de) 1972-07-20
NL7117483A (es) 1972-07-04
JPS535816B1 (es) 1978-03-02
IT945668B (it) 1973-05-10
CA949122A (en) 1974-06-11

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