EP0541841A1 - Verfahren und Gerät zum elektrostatischen Bildaufbau - Google Patents

Verfahren und Gerät zum elektrostatischen Bildaufbau Download PDF

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Publication number
EP0541841A1
EP0541841A1 EP91119221A EP91119221A EP0541841A1 EP 0541841 A1 EP0541841 A1 EP 0541841A1 EP 91119221 A EP91119221 A EP 91119221A EP 91119221 A EP91119221 A EP 91119221A EP 0541841 A1 EP0541841 A1 EP 0541841A1
Authority
EP
European Patent Office
Prior art keywords
electrode
gas
discharge region
cartridge
nitrogen
Prior art date
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.)
Withdrawn
Application number
EP91119221A
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English (en)
French (fr)
Inventor
Orrin D. Christy
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Moore Business Forms Inc
Original Assignee
Moore Business Forms Inc
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Filing date
Publication date
Application filed by Moore Business Forms Inc filed Critical Moore Business Forms Inc
Priority to EP91119221A priority Critical patent/EP0541841A1/de
Publication of EP0541841A1 publication Critical patent/EP0541841A1/de
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/385—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material
    • B41J2/41—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material for electrostatic printing
    • B41J2/415—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective supply of electric current or selective application of magnetism to a printing or impression-transfer material for electrostatic printing by passing charged particles through a hole or a slit

Definitions

  • IDAX and MIDAX printing techniques are commercial electrographic imaging techniques that utilize what is referred to as silent electric discharge.
  • an ion cartridge is mounted adjacent an imaging drum. The drum then moves into contact with a transfer sheet (e.g. paper).
  • the conventional cartridges utilized in these printing systems include first and second electrodes, typically called the driver and control electrodes, separated by a solid dielectric member, such as a sheet of mica.
  • the control electrode typically in the form of control fingers, defines an edge surface disposed opposite the driver electrode to define a discharge region at the junction of the edge surface and the solid dielectric member.
  • An alternating potential is applied between the driver and control electrodes of sufficient magnitude to induce charged particle producing electrical discharges in the discharge region, and means are provided for applying a charged particle extraction potential between the control electrode and a further electrode, so that imaging occurs on the imaging drum, or paper or like dielectric moving past the ion cartridge.
  • a screen electrode is also provided, between the imaging drum and the control electrode, and separated by an insulating spacer from the control electrode.
  • a commercial ion cartridge is typically constructed of a plurality of driver, control, and screen electrode units, in a matrix form.
  • red death By-products formed in the ionization process, such as oxides, build up on the cartridge control fingers which can cause an uneven rush of electrons and negative ions upon application of the extraction voltage.
  • white death Another mode of failure is euphemistically referred to as “white death”.
  • white crystals which typically are nitrates, build up on the screen electrode thereby creating a dielectric layer and causing an electrical defocussing of the electron and ion stream as it exits the cartridge.
  • black death A third typical mode of failure, euphemistically referred to as “black death” is caused by premature catastrophic failure of the cartridge when conductive toner is sucked up into the cartridge and creates unwanted electrically conductive paths and also localized heating.
  • the mechanisms by which at least red and white death occur are dependent upon the characteristics of the atmosphere from which the ions are produced by the ion cartridge.
  • the atmosphere is typically normal air, although it may be contaminated with ammonia, benzene, or other gases depending upon the particular plant in which the system is utilized.
  • Nitrogen, oxygen, and water vapor are the major components of the atmosphere, and during operation of the MIDAX printers after one stream of electrons and ions is created and extracted from the cartridge new air replaces that which was lost from the cartridge.
  • Most of the problems of ion cartridge aging are caused by compounds made of or initiated by oxygen and/or water vapor, and therefore the process can be slowed or even eliminated by the replacement of the air around the ion cartridge with appropriate other gases.
  • Gases that are particularly effective in the practice of the invention are nitrogen, mixtures of nitrogen and helium, and mixtures of nitrogen with argon, xenon, neon, and/or krypton. It has been found that completely dry pure nitrogen is not particularly effective since nitrogen is not easily ionized, and therefore there must be some "catalyst" present to enhance the nitrogen ionization. However the catalyst must be present in small enough amounts so that arcing does not occur, since arcing can be destructive and reduce cartridge life. While water vapor that naturally occurs can provide this catalyst effect, it is desirable for other reasons to keep the amount of water vapor to a minimum. Therefore it is most desirable to add another gas, such as a noble gas, to the nitrogen.
  • another gas such as a noble gas
  • helium can be effective as a catalyst for nitrogen ionization
  • Argon, xenon, neon, and krypton do not have that effect, however, yet they provide an effective catalyst for nitrogen ionization.
  • the amounts of argon, neon, krypton, or xenon must be controlled, however, to make sure that they are low enough so that arcing does not occur.
  • nitrogen is mixed with argon, xenon, neon, or krypton so that there is a volume ratio of about 5 - 1 to about 20 - 1 of nitrogen to other gas.
  • the invention is most effective in some actual operating environments when nitrogen and argon are mixed at a ratio of about 10 to 1.
  • the gas mixture is supplied to the discharge region at a rate of about 4.75-6.25 cubic feet per hour, typically about .5 cubic feet per hour of argon, xenon, neon, or krypton, and about 5 cubic feet per hour nitrogen.
  • a number of particularly advantageous mechanisms for introducing the gas to the discharge region are provided according to the invention.
  • Black death can be significantly reduced if the gas is introduced through the insulating spacer between the control electrode and the screen electrode.
  • the gas is typically introduced at a pressure above atmospheric pressure so that a positive pressure is provided in this area, and conductive toner can therefore not be easily sucked into the ion cartridge.
  • the gas may be injected through a plenum and holes spaced about one-half inch along a pre-existing cartridge mounting rail, typically the first rail in the direction of rotation of the imaging drum.
  • a pair of gas manifolds may be provided at opposing ends of the imaging drum, and a pair of spray tubes extending between the gas manifolds with a plurality of openings provided along their length.
  • the gas is then supplied by regulators and conduits to the gas manifolds, and thus introduced uniformly between the ion cartridge and the imaging drum.
  • an improved method of generating charged particles for electrostatic imaging which comprises the following steps: applying an alternating potential between a first electrode substantially in contact with one side of a solid dielectric member and a second electrode substantially in contact with an opposite side of the solid dielectric member, said second electrode having an edge surface disposed opposite said first electrode to define a discharge region at the junction of the edge surface and the solid dielectric member, to induce charged particle producing electrical discharges in said air region between said solid dielectric member and the edge surface of said electrode; applying a charged particle extraction potential between said second electrode and a further electrode member to extract charged particles produced by the electrical discharges in said air region; and applying the external charged particles to a further member to form an electrostatic image; wherein the improvement comprises supplying a controlled gas to the discharge site to displace at least some of the air during charged particle generation, said controlled gas being selected from the group consisting of nitrogen, elemental noble gasses, mixtures of elemental noble gasses, and mixtures of nitrogen with one or more elemental noble gasses.
  • improved apparatus for generating electrostatic images of the type including a solid dielectric member.
  • the apparatus comprises a "driver" electrode substantially in contact with one side of the solid dielectric member; a “control” electrode substantially in contact with an opposite side of the solid dielectric member, with an edge surface of said control electrode disposed opposite said driver electrode to define a discharge site at the junction of said edge surface and said solid dielectric member; means for applying an alternating potential between said driver and control electrode of sufficient magnitude to induce charged particle producing electrical discharges in said discharge site between the solid dielectric member and the edge surface of the control electrode; means for applying a charged particle extraction potential V c between the control electrode and a further electrode member to extract ions produced by the electrical discharges in said air region and apply these charged particles to a dielectric surface to form an electrostatic image thereon, a third (“screen”) electrode; a solid dielectric layer separating said screen electrode from the control electrode and the solid dielectric member; and a source of "screen” voltage V s between the screen electrode and the
  • FIGURE 1 An exemplary apparatus according to the present invention is shown generally by reference numeral 10 in FIGURE 1.
  • the main components include the silent electric discharge ion generating system 11, and an imaging drum 12 or like device for moving a dielectric, such as dielectric belt or dielectric paper web 13 or dielectric surface of drum 12, past the SED apparatus 11.
  • a dielectric such as dielectric belt or dielectric paper web 13 or dielectric surface of drum 12
  • One of the major components of the SED apparatus 11 comprises the ion cartridge 14 which is mounted by a cartridge mounting block 15 within a casing defined by driver printed circuit board 16 and cartridge connectors 17.
  • the structures 16, 17 are supported by a pair of cartridge mounting rails 18, 19 that are elongated in the direction of elongation of the drum 12 and the ion cartridge 14.
  • the drum 12 is mounted for rotation in the direction A by a shaft, bearings, and like conventional components, and so that it is spaced only a small distance from each of the rails 18, 19, defining gaps 20, 21 therewith.
  • the gaps 20, 21 have a width of less than about .002 inches (0.051 mm).
  • An interior volume 22 is provided between the ion cartridge 14 and the imaging drum 12.
  • the ion cartridge 14 is of conventional construction, such as shown in U.S. patents 4,155,093, 4,160,257, 4,267,556, and/or 4,381,327.
  • FIGURE 2 very schematically illustrates one component of the ion cartridge 14, there being many such components arranged throughout the length of the ion cartridge 14 (typically in matrix form) to provide electrostatic charges to the dielectric web or belt 13.
  • the major components of the cartridge 14 schematically illustrated in FIGURE 2 comprise a first or driver electrode 24, a second or control electrode 25 typically formed by a plurality of control fingers, and a solid dielectric member 26 disposed therebetween.
  • the member 26 is mica in commercial installations, however according to the invention improved performance and longevity are possible so that other solid dielectric members besides mica may be practical.
  • a high voltage alternating potential 28 is applied between the driver and control electrodes 24, 25 to cause the formation of a pool or plasma of positive and negative charged particles in the region adjacent the dielectric 26 at an edge surface of the control electrode 25, which charged particles may be extracted to form a latent electrostatic image on the dielectric belt or web 13 or drum 12 periphery.
  • Charged particles of a given polarity may be extracted from the plasma by applying a bias potential 29 of appropriate polarity between the second electrode 25 and a further electrode, which typically would comprise the image drum 12 itself.
  • a screen electrode 31 defining a screen aperture 32 is provided spaced by an electrical insulator 30 from the second electrode 25.
  • the screen voltage should be in a relatively narrow range, e.g. -400 to -900.
  • the screen voltage is determined in part by the distance of the screen 31 from the drum 12. At a distance of 0.0010 inches (0.025 mm), the optimum screen voltage is about -700, and could be increased to about -800 before arcing occurs.
  • constant power supply 33 (typically a voltage of about -700) and variable power supply 34, and a switch 27, are provided in addition to power supply 29 (typically a voltage of about -275).
  • the power supply 34 typically has a range of about +200 to about +300 (e.g. about +250).
  • the screen electrode 31 provides an electrostatic lensing action preventing accidental image erasure and focussing of the electrostatic discharge onto the drum 12 periphery.
  • a dielectric belt or web 13 need not pass past the ion cartridge 14, but rather the peripheral surface of the imaging drum 12 is dielectric, and that surface moves into operative association with a receptor sheet, such as a paper sheet, which cooperates with a transfer roll.
  • the apparatus comprises means for supplying a control gas to the discharge region during the generation of charged particles.
  • the control gas which in the FIGURE 1 embodiment is supplied directly to the volume 22 -- comprises a gas selected from the group consisting essentially of nitrogen, elemental noble gases, mixtures of elemental noble gases, and mixtures of nitrogen with one or more elemental noble gases. It is not essential that all contaminants be removed from the gases, and in fact where pure nitrogen is utilized it is necessary that water vapor, or some other catalyst to facilitate nitrogen ionization, be present in order for the system to work properly. However it has been found that almost 100% pure nitrogen supplied as illustrated in FIGURE 1, or in a like manner, combined with the natural water vapor from the paper or other components introduced into the system, works satisfactory to at least enhance print uniformity.
  • Nitrogen mixed with helium is also effective, however in commercial installations where an operator will be located adjacent to the printing apparatus 10 helium is not desirable since by-product gases are produced which can have undesirable side effects when inhaled, and thereby pose a safety hazard. It has been found that it is particularly desirable, however, to provide a particular mixture of nitrogen with one or more of argon, krypton, xenon, or neon, most preferably argon.
  • the amount of noble gas to be mixed with nitrogen should be enough to provide a catalyst for nitrogen ionization.
  • elemental noble gas present in too large a quantity will cause arcing to occur, the amount of noble gas must be limited by that criteria.
  • a mixture of nitrogen and one or more of argon, krypton, xenon, or neon gases --particularly argon -- is most suitable, the volume ratio of nitrogen to other gas being in the range of 5 to 1 to 20 to 1, most desirably about 10 to 1.
  • the flows of the gases making up the mixture are controlled so that the total gas mixture flow to the discharge region is at a rate of about 4.75-6.25 cubic feet per hour, most typically by supplying nitrogen at about 5 cubic feet (0.14 cu. metres) per hour and the other gas, e.g. argon, at about .5 cubic feet (0.014 cu. metres) per hour.
  • nitrogen at about 5 cubic feet (0.14 cu. metres) per hour
  • the other gas e.g. argon
  • Supply of gas to the volume 22 in the FIGURE 1 embodiment is provided by utilizing the pre-existing cartridge mounting rail 18 at the "first" portion of the imaging drum 12 as it rotates in direction A into the volume 22, so that gas passes with the rotating drum toward the gap 21.
  • This is preferably provided by forming a plenum 35 in the rail 18, with a plurality of through-extending openings or jets 36 from the plenum 35 to the volume 22, preferably the openings or jets 36 being spaced from each other about one half inch along the length of the rail 18.
  • a conduit 37 leading from a source 38 of pressurized nitrogen, or other gas pursuant to the invention, supplies the controlled gas to the plenum 35.
  • the source 38 can be either compressed nitrogen or like gas, or a liquid nitrogen dewer, or a Prima Alpha Separated nitrogen filter attached to a compressed air source.
  • the apparatus 10 of FIGURE 1 can greatly assist in extending the life of the ion cartridge. That is the avoidance of red death and white death may be provided. However a small amount of air, and other materials, may still pass into the volume 22, and therefore it is possible that conductive toner particles may accidentally be drawn into the volume 22, which conductive toner would burn and result in premature catastrophic failure of the cartridge 14. In order to prevent this "black death", the apparatus illustrated in FIGURE 3 may be utilized.
  • FIGURE 3 drawing elements that are comparable to those in the FIGURES 1 and 2 embodiment are illustrated by the same reference numeral only preceded by a "1".
  • the first or driver electrode 124 is shown mounted on a conventional backing insulator 40, which in turn is connected to an aluminum backbone 41.
  • the mica dielectric member 126 is disposed between the driver electrode 124 and the control electrode fingers 125, with an insulating spacer 130 separating the screen electrode 131 from the control fingers 125.
  • the nitrogen or like gas under pressure (that is greater than ambient pressure) is introduced into the discharge region through the insulating spacer 130, having a vector generally parallel to the control fingers 125, by the openings or jets 136 connected to the plenum 135.
  • the gas for ionization at the discharge region flows outwardly through the opening 132 in the screen electrode 131, along with the ions, and since a positive pressure is maintained at the discharge region it is extremely unlikely that conductive toner particles could enter that area and thereby cause "black death".
  • FIGURES 4 and 5 is still another embodiment of the apparatus for supplying the desired gases to the discharge region, according to the invention.
  • structures comparable to those in the FIGURES 1 and 2 embodiment are illustrated by the same reference numeral only preceded by a "2".
  • the ion cartridge 214 is shown in operative association with a support 45, which provides a positive electrical connection adjacent the image drum 212. Gas is supplied via the gas manifolds 47, 48 which are mounted on opporegion ends of the cartridge 214 and drum 212.
  • a pair of spray tubes 49, 50 having a plurality of openings 51, 52 respectively therein extend between the manifolds 47, 48 and supply gas directly to the "top" of the drum 212 (as oriented in FIGURE 4), and just below the ion cartridge 214, to provide the vast majority of the gas at the discharge region.
  • Gas is supplied to the manifolds 47, 48 by conduits 54, 55 which are connected to a tee fitting 56, which in turn is connected by conduit 58 to a second tee fitting 59 (see FIGURE 5).
  • a source of nitrogen under pressure, 61, and a source of argon under pressure, 62 are provided to supply the ionizing gas.
  • the sources 61, 62 are connected by conventional regulators and metering devices 63, 64 to the tee fitting 59.
  • the regulator/metering devices 63, 64 control the flow rates of nitrogen and argon (or xenon, krypton, or neon) so that they are in the appropriate range.
  • the board 45 may have spring loaded pins 67 for engaging 214, and electrical connectors 68 for the drive electrode of the ion cartridge.
  • the ratio of nitrogen to argon (or xenon, krypton, or neon) is about 5 to 1 to 20 to 1, most preferably about 10 to 1.
  • the flow rate is regulated so that the gas mixture supplied to the region by the tubes 49, 50 is (for the FIGURES 4 and 5 embodiment of apparatus) at a rate of about 4.75-6.25 cubic feet (0.134 to .177 cu. metres) per hour. This rate may change depending upon the particulars of the geometry for applying the gas to the discharge region, but would be at an equivalent range taking into account the differences in the supply apparatus. Most desirably, the nitrogen would be supplied at about 5 cubic feet (0.14 cu.
  • the nitrogen flow rate could vary about plus or minus 10%, and the argon flow rate could vary about plus or minus 50%. It is necessary, however, that the amount of argon, or like gas, be supplied to the nitrogen stream so as to be effective to provide a catalyst for nitrogen ionization; however the amount must be low enough to prevent arcing since arcing more readily occurs the higher the percentage of argon or the like.
  • control of internal operating voltages may be effected from an operator control panel (not shown).
  • the operator notices that the print quality is degrading, he can increase the voltage to ion cartridge 14, and operate the regulators 63, 64 to close of the cylinders 61, 62. While good quality printing (due to the increased voltage) continues, he can then replace the gas bottles 61, 62, and once he reestablishes the gas supply utilizing regulators 63, 64, he can then reduce the voltage back to normal. In this way the system can be continuously run without a degradation in print quality while changeover of gas supplies takes place.

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  • Control Or Security For Electrophotography (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
EP91119221A 1991-11-12 1991-11-12 Verfahren und Gerät zum elektrostatischen Bildaufbau Withdrawn EP0541841A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP91119221A EP0541841A1 (de) 1991-11-12 1991-11-12 Verfahren und Gerät zum elektrostatischen Bildaufbau

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP91119221A EP0541841A1 (de) 1991-11-12 1991-11-12 Verfahren und Gerät zum elektrostatischen Bildaufbau

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EP0541841A1 true EP0541841A1 (de) 1993-05-19

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0876918A3 (de) * 1997-05-08 1999-08-04 Heidelberger Druckmaschinen Aktiengesellschaft Elektrostatischer Schreibkopf für eine elektronische Druckmaschine
WO2012017268A1 (en) 2010-08-04 2012-02-09 Triakon Nv Print head element, print head and ionographic printing apparatus

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2148001A1 (de) * 1971-09-25 1973-03-29 Agfa Gevaert Ag Verfahren zur elektrographischen aufzeichnung von ladungsbildern
DE2515578A1 (de) * 1975-04-10 1976-10-21 Siemens Ag Elektrographische schreibvorrichtung mit gesteuerter gasentladung
DE2645928A1 (de) * 1976-10-12 1978-04-13 Agfa Gevaert Ag Verfahren zur aenderung der gradation bei der elektrostatografischen aufzeichnung von halbtonbildern

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2148001A1 (de) * 1971-09-25 1973-03-29 Agfa Gevaert Ag Verfahren zur elektrographischen aufzeichnung von ladungsbildern
DE2515578A1 (de) * 1975-04-10 1976-10-21 Siemens Ag Elektrographische schreibvorrichtung mit gesteuerter gasentladung
DE2645928A1 (de) * 1976-10-12 1978-04-13 Agfa Gevaert Ag Verfahren zur aenderung der gradation bei der elektrostatografischen aufzeichnung von halbtonbildern

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0876918A3 (de) * 1997-05-08 1999-08-04 Heidelberger Druckmaschinen Aktiengesellschaft Elektrostatischer Schreibkopf für eine elektronische Druckmaschine
WO2012017268A1 (en) 2010-08-04 2012-02-09 Triakon Nv Print head element, print head and ionographic printing apparatus

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