US3575502A - Electrophotographic copying arrangement - Google Patents

Electrophotographic copying arrangement Download PDF

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Publication number
US3575502A
US3575502A US737484A US3575502DA US3575502A US 3575502 A US3575502 A US 3575502A US 737484 A US737484 A US 737484A US 3575502D A US3575502D A US 3575502DA US 3575502 A US3575502 A US 3575502A
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United States
Prior art keywords
charging device
copy carrier
charge
copy
throttling
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.)
Expired - Lifetime
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US737484A
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English (en)
Inventor
Rudolf Eppe
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.)
Agfa Gevaert AG
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Agfa Gevaert AG
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Publication date
Priority claimed from DE19671572330 external-priority patent/DE1572330C3/de
Application filed by Agfa Gevaert AG filed Critical Agfa Gevaert AG
Application granted granted Critical
Publication of US3575502A publication Critical patent/US3575502A/en
Anticipated expiration legal-status Critical
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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
    • G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
    • G03G15/16—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S271/00—Sheet feeding or delivering
    • Y10S271/90—Stripper

Definitions

  • Electrophotographic copiers are known in which a cylinder having a peripheral layer of a photoconductive material is first electrostatically charged and then exposed by a projected image so that a latent image is formed. The latent image is developed by application of a powder which is attracted by the electrostatic force of the latent image. A powder image is thus formed which is transferred to a copy sheet which is electrostatically charged by a corona charging device.
  • Electrophotographic copiers of this type require the charging of the copy sheet from its rear face substantially at the voltage and with the polarity of the charged latent image of the photoconductive layer. Electrostatic forces are thus created which cause attraction between the photoconductive layer and the copy sheet so that the copy sheet tends to adhere to the photoconductive layer of the cylinder.
  • blowers are provided for producing a high-pressure air stream by which the copy sheet is separated from the cylinder surface.
  • lt has also been' proposed to strip the copy sheet from the cylinder surface by stripping devices or gripping devices.
  • the constructions of the prior art serving this purpose are rather expensive, take up much space, and are not absolutely reliable.
  • Another object of the invention is to charge the copy carrier with a charge having opposite polarity than the charge by which the powder image is transferred to the copy carrier so that the charges neutralize each other and no electrostatic attraction occurs between the copy carrier and the surface transporting the powder image.
  • Another object of the invention is to provide a transfer charging device and a compensating charging device for charging the copy carrier with substantially equal charges of opposite polarity so that the copy carrier is not attracted by an electrostatic force.
  • an embodiment of. the invention comprises transporting means, such as a cylinder having a movable surface; means for forming on the surface a latent image, for example by projecting an image onto a charged area of the surface; developing means for applying a powder to the latent image to form a powder image; a transfer charging device including a first corona charging device for charging a copy carrier or copy sheet with a first charge having a first polarity so that the powder image is transferred to the charged copy carrier; and a compensating charging device, such as a second corona charging device, for charging the charged copy carrier with a second charge having an opposite polarity.
  • the second charge is substantially equal to the first charge or slightly smaller, so that the first charge is substantially neutralized. Consequently, no electrostatic attractive force develops between the copy carrier and the surface of the transporting means, and the copy carrier does not adhere to the surface.
  • the copy carrier is first transported ⁇ past the transfer charging device and then past the compensating charging device, each of which produces an ion stream.
  • the charges produced on the copy carrier by the ion'streams while the copy carrier passes the transfer charging device and the compensating charging device, respectively, are substantially equal to effect neutralizaton of the opposite charges.
  • the compensation charge must be correctly measured in order to prevent that the compensating charge substantially exceeds the transfer charge and again causes electrostatic attraction of the copy carrier.
  • the desired compensation of the charges can be obtained in accordance with one embodiment of the invention by providing the transfer charging device and the compensating charging device with throttling means for throttling the stream of ions from the charging devices to the copy carrier. ln accordance with the invention, the ion stream of the compensating charging device is throttled to a greater degree than the ion stream of the transfer charging device, and also vof the charging device which produces the charged area on which the latent image is formed.
  • a control grid of known construction may be used for throttling corona charging devices.
  • control grids of the corona charging device which produces the charged area on which the latent image is formed, and the control grid ofthe transfer charging device by which the powder image is transferred to the copy carrier, are advantageously connected with a voltage source providing +600 to +800 v., while the controlgrid of the compensating corona charging device is connected to ground or to zero voltage.
  • the grounded housing of each corona charging device is provided with a slot facing the layer which is to be charged.
  • the slots through which the ion stream of the compensating corona charging device passes is narrower than the slot through which the ion stream of the transfer corona charging device passes so that Y device, and/or. the ion stream of the compensating charging ⁇ device may be throttled .to a higher degree than the ion stream' the compensating charge ⁇ does not exceed the charge of opposite polarity required for the transferof the powder image.
  • the transfer charge of the copy carrier When the transfer charge of the copy carrier is compensated and neutralized in accordance with the invention, it can be separated from the cylinder by a conventional stripper.
  • a low-pressure airstream is directed towards the leading edge of the copy carrier or copy sheet which tends to adhere to the surface. of the transporting cylinder.
  • a very small pressure of about 2 mm. to 3 mm. hydraulic head is sufficient, so that it is apparent that no mechanical separation is effected by the low-pressure airstream. lt is therefore assumed that the surprising effect of the low-pressure airstream is caused by an improvement of the compensation of the opposite charges by the additional movement. of the ion stream caused by the low-pressure airstream.
  • the opposite and equal voltages applied to the transfer charging device and to the compensating charging device are preferablyfobtained by connecting the two charging devices, respectively, through two rectifiers to a transformer, the rectifiers being connected to block pulses of opposite polarity so that a positive voltage is applied to the transfer charging device and a negative voltage is applied to the compensating charging device. Since the two voltages are equal, the compensatingl chargingtdevice may be spaced a ⁇ greater distance from the copy carrier than the transfer charging claims.
  • the invention itself, however, both as to. its.
  • An area of surface la is charged by the corona charging device 2 to a voltage of .+600 v. to +800 v. and moves into a region of an objective 3 which forms an image of an original or master 4 illuminated by rod-shaped lamps 5 and 6 and being carried by a transparent slide 7.
  • a rope attached to cylinder l and slide 7, and passing over guide rollers, causes movement of the slide 7 with the master 4 in the direction of the arrow B when cylinder l rotates in the direction of the arrow A.
  • Master 4 and surface la move at the same speed in opposite directions so that an image of the master is formed on the surface la whereby a latent image of master 4 is formed on the charged area of surface la.
  • the latent image passes developing means 8 by which an electrostatic powder is applied to the charged surface area and adheres to the latent image so that a powder image is formed.
  • the charged area with the powder image is brought into contact with a copy carrier or copy sheet fed by a feeding means 9 from the top of a stack of copy sheets 10 in the direction of the arrow C.
  • the copy carrier While the copy carrier moves together with surface la, in contact with the charged area and with the powder image, it passes a corona charging device 11 whose discharge electrode 11b is connected by resistor 26 to rectifier 2l which supplies a positive voltage between 600 v. and 800 v. so that a stream of ions passes through a slot in the housing of corona charging device 1l toward the copy sheet and charges the rear face of the same with +600 v. Due to this charge, the powder of the powder image is attracted and is transferred from surface la to the front face of the copy sheet.
  • the charged area of surface 1a passes a source of light l2 which effects discharge of the positive charge of the charged surface area whereupon surface la passes a rotary cleaning device 13 which removes all powder still adhering to surface la so that surface la can again be charged by corona charging device 2, and another copying operation started.
  • a further corona charging device 14 is disposed following corona charging device ll in the direction of movement of surface la.
  • the housing of corona charging device 14 is grounded, and its discharge electrode l4b connected by a resistor 27 to a rectifier 22 which produces a negative voltage.
  • the corona charging device 14 has a slot 14a through which an ion stream passes so that the copy sheet receives a negative charge for neutralizing the positive charge produced by the corona charging device 1l.
  • corona charging device 14 compensates the charge produced by the corona charging device l1 for the purpose of transferring the powder image, and therefore charging device ll will be referred to hereinafter as transfer charging device, and charging device 14 will be referred to as compensating charging device.
  • the ion streams By selecting the width of slot 14a of the compensating charging device 14 to be smaller than the width of slot 11a of the transfer charging device ll, and also than the width of slot 2a of charging device 2, the ion streams have a corresponding width in the direction of movement of surface la and produce corresponding charges so that by selection of the free width of slots 2a and 11a, the desired charge of between 600 and 800 v. is obtained.
  • the ion stream of compensating charging device 14 emitted by discharge electrode 14h is limited by the narrower opening 14a toa greater degree than the ion stream of the preceding charging devices 2 and 1l.
  • compensating charging device 14 is disposed at a greater distance from the copy sheet than transfer charging device l1, and also at a greater distance than charging device 2 is spaced from surface la.
  • the compensating charging device 14 cannot charge the copy sheet to a negative voltage having a similar value as the positive charge produced by the transfer charging device 14. Only compensation and neutralization of the positive charge required for the transfer of the powder image is effected by the compensating charging device 14 due to its narrower slot 14a and the greater spacing from the copy sheet.
  • the neutralized copy sheet is no longer electrostatically attracted to the cylinder surface la, and drops off the same so that it can be supplied to a heating device l5 by which the transferred powder image on the copy sheet is pennanently fixed to the same.
  • the separation of the copy sheet from cylinder surface la is further improved by a low-pressure stream of air blown out of a nozzle 16 whose discharge opening 16a extends over the entire axial length of cylinder 1.
  • Nozzle 16 is disposed closely adjacent surface la, and the airstream is blown in tangential direction of cylinder surface la toward the leading edge of the copy sheet which moves in the direction C.
  • the pressure of the airstream is only 2 mmA to 3 mm. hydraulic head, so that it is not the mechanical power of the airstream by which a copy sheet is separated from the cylinder surface. Rather, the effective separating action of the low-pressure airstream is due to an improvement of the compensation of the transfer charge of the copy sheet by the additional movement of the ion stream of the compensating charging device 14 produced by the low-pressure airstream.
  • a transformer l7 is connected to a voltage source 18 and 19 of an alternating voltage of 220 v. and 50 Hz.
  • the secondary winding of transformer 17 produces a voltage between 5000 and 6000 v. and has one grounded terminal, and a terminal connected by line 20 to rectifier 2l which blocks the negative pulses of the alternating current and to a rectifier 22 which blocks the positive pulses of the alternating current so that rectifier 2l supplies a positive voltage to charging devices 2 and ll, while rectifier 22 supplies a negative voltage to charging device 14.
  • Equal voltages of opposite polarity are supplied to the transfer charging device 1l and to the compensating charging device 14.
  • Electrophotographic copying arrangement comprising, in combination, transporting means having a movable surface; means for forming on said surface a latent image; developing means for applying a powder to said latent image to form a powder image on said surface; means for feeding a chargeable copy carrier to said surface in the region of said powder image; a transfer charging device emitting a first ion stream toward said copy carrier for charging said copy carrier with a first charge having a first polarity so that said powder image is transferred to said charged copy carrier and an electrostatic force attracts said charged copy carrier to said surface; and a compensating charging device emitting a second ion stream toward said copy carrier for charging said charged copy carrier during passage of said compensating charging device by said copy carrier with a second charge having a second polarity opposite to said first polarity and being substantially equal to said first charge produced by said first ion stream during passage of said transfer charging device by said copy carrier for at least substantially neutralizing said first charge so that said copy carrier does not adhere to said surface of said transporting means.
  • said transfer charging device includes first throttling means for throttling said first ion stream; wherein said compensating charging device includes second throttling means for throttling said second ion stream to a greater degree than said first ion stream is throttled by said first throttling means.
  • said means forforming a latent image include a third charging device emitting a third ion stream directed at said surface for producing a charged area thereon, and including third throttling means for throttling said third ion stream to a lesser degree than said second throttling means throttles said second Iion stream, and means for projecting an image onto said charged area.
  • said transfer charging device includes a first'throttling slot for throttling said first ion stream; wherein said compensating charging device includes a second throttling slot narrower than said first throttling slot for throttling said second ion stream to a greater degree than said first ion stream is throttled by said first throttling slot.
  • said transfer charging device includes first throttling means for throttling said first ion stream; wherein said compensating charging device includes second throttling means for throttling said second ion stream to a greater degree than said first ion stream is throttled by said first throttling means; and comprising means for applying equal voltages of opposite polarity to said transfer charging device and said compensating charging device, respectively.
  • Electrophotographic copying arrangement comprising, in combination, transporting means having a movable surface; means for forming on said surface a latent image; developing means for applying a powder to said latent image to form a powder image on said surface; means for feeding a chargeable copy carrier to said surface in the region of said powder image; a transfer charging device disposed at a first distance from said copy carrier for charging said copy carrier with a first charge having a first polarity so that said powder image is transferred to said charged copy carrier and an electrostatic force attracts said charged copy carrier to said surface; and a compensating charging device disposed at a second distance from said copy carrier for charging said charged copy carrier with a second'charge having a second polarity opposite to said first polarity for at least substantially neutralizing said first charge so that said copy carrier does not adhere to said surface of said transporting means. Said second distance being greater than said first distance whereby the same voltage applied to said charging devices produces a lesser second char e.
  • opying arrangement as claimed in claimv comprising a transformer adapted to be connected to a source of alternating voltage; first and second rectifiers connected with said transformer to block negative pulses and positive pulses, respectively, said first and second rectifiers being, respectively, connected with said transfer charging device and with said compensating charging device so that said transfer charging device produces a positive first charge and said compensating charging device produces a negative second charge of said copy carrier.
  • Electrophotographic copying arrangement comprising, in combination, transporting means including a rotary cylinder having a peripheral surface moving in one direction; means for forming on said surface a latent image; developing means for applying a powder to said latent image to form a powder image on said surface; means for feeding chargeable copy carrier to said surface; a transfer charging device for charging said copy carrier with a first charge having a first polarity, said feeding means feeding said copy carrier to said surface in the region of said transfer charging device so that said powder image is transferred to said charged copy carrier and an electrostatic force attracts said charged copy carrier to said surface; a compensating charging device disposed following said transfer charging device in said one direction for charging said charged copy carrier with a second charge having a second polarity opposite to said first polarity for at least substantially neutralizing said first charge so that said copy carrier does not adhere to said surface of said transporting means; and blower means for blowing a low pressure stream of air toward the leading edge of said copy carrier and past said compensating charging device.
  • Electrophotographic copying arrangement comprising, in combination, transporting means having a movable surface; means for forming on said surface a latent image; developing means for applying a powder to said latent image to form a powder image on said surface; means for feeding a chargeable copy carrier to said surface; a transfer charging device for charging said copy carrier with a first charge having a first polarity, said feeding means feeding said copy carrier to said surface in the region of said transfer charging device so that said powder image is transferred to said charged copy carrier and an electrostatic force attracts said charged copy carrier to said surface; and a compensating charging device for charging said charged copy carrier with a second charge having a second polarity opposite to said first polarity for at least substantially neutralizing said first charge so that said copy carrier does not adhere to said surface of said transporting means; and blower means for blowing a low pressure stream of air toward the copy carrier on said surface for separating the same from said surface.
  • Electrophotographic copy arrangement comprising, in combination, transporting means having a movable surface; means for forming on said surface a latent image; developing means for applying a powder to said latent image to form a powder image on said surface; means for feeding a chargeable copy carrier to said surface in the region of said powder image; a transfer charging device for charging said copy carrier with a first charge having a first polarity so that said powder image is transferred to said charged copy carrier and an electrostatic force attracts said charged copy carrier to said surface; a compensating charging device emitting an ion stream toward said copy carrier for charging said charged copy carrier with a second charge having a second polarity opposite to said first polarity for at least substantially neutralizing said first charge so that said copy carrier does not adhere to said surface of said transporting means; and blower means for blowing a low pressure stream of air past said compensating charging device toward said fed copy carrier and into said ion stream so as to displace said ion stream for separating said copy carrier from said surface, the pressure of said stream

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Combination Of More Than One Step In Electrophotography (AREA)
US737484A 1967-06-15 1968-06-17 Electrophotographic copying arrangement Expired - Lifetime US3575502A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19671572330 DE1572330C3 (de) 1967-06-15 1967-06-15 Elektrofotografisches Kopiergerät

Publications (1)

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US3575502A true US3575502A (en) 1971-04-20

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US737484A Expired - Lifetime US3575502A (en) 1967-06-15 1968-06-17 Electrophotographic copying arrangement

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US (1) US3575502A (enrdf_load_stackoverflow)
BE (1) BE716658A (enrdf_load_stackoverflow)
CH (1) CH476332A (enrdf_load_stackoverflow)
FR (1) FR1568680A (enrdf_load_stackoverflow)
GB (1) GB1242072A (enrdf_load_stackoverflow)
HK (1) HK79276A (enrdf_load_stackoverflow)
NL (1) NL159205B (enrdf_load_stackoverflow)
SE (1) SE338508B (enrdf_load_stackoverflow)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3811670A (en) * 1972-06-19 1974-05-21 Xerox Corp Electrostatographic apparatus with air baffle
US3851230A (en) * 1972-06-09 1974-11-26 Ricoh Kk Electrostatic transfer-printing sheet stripping device
US3870515A (en) * 1970-05-20 1975-03-11 Xerox Corp Method for electrostatic paper stripping by neutralization of transfer charge
US3970381A (en) * 1973-02-26 1976-07-20 Xerox Corporation Method and apparatus for xerographic reproduction
US4025180A (en) * 1973-10-30 1977-05-24 Minolta Camera Kabushiki Kaisha Transfer type electrophotographic copying apparatus
US4027960A (en) * 1975-08-06 1977-06-07 Xerox Corporation Transfer system for electrostatic reproduction machine
US4086010A (en) * 1976-11-01 1978-04-25 Xerox Corporation Illumination system utilizing two opposing DC lamps with an optimum barrel-shaped slit
USRE31499E (en) 1976-11-01 1984-01-17 Xerox Corporation Illumination system utilizing two opposing DC lamps with an optimum barrel-shaped slit
US4482240A (en) * 1981-06-24 1984-11-13 Canon Kabushiki Kaisha Electrophotographic process utilizing electrostatic separation and apparatus therefor
US4579441A (en) * 1982-12-03 1986-04-01 Xerox Corporation Detacking apparatus
US4640606A (en) * 1983-02-15 1987-02-03 Sharp Kabushiki Kaisha Corona discharger for separating copy paper from photoreceptor in electrophotographic copying machine
US4676627A (en) * 1982-12-09 1987-06-30 Canon Kabushiki Kaisha Image forming apparatus
US4728880A (en) * 1986-11-28 1988-03-01 Eastman Kodak Company Multiple voltage-pulsed corona charging with a single power supply
US4801975A (en) * 1986-04-18 1989-01-31 Mita Industrial Co. Ltd. Eraser lamp and transparent guide plate in electrostatic image transfer
US5450179A (en) * 1994-02-28 1995-09-12 Eastman Kodak Company Active charging to prevent image disruption
US20040114956A1 (en) * 2002-12-13 2004-06-17 Xerox Corporation Bias charge roller with optimally induced AC corona

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3147679A (en) * 1961-12-18 1964-09-08 Ibm Electrostatic image transfer processes and apparatus therefor

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3147679A (en) * 1961-12-18 1964-09-08 Ibm Electrostatic image transfer processes and apparatus therefor

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3870515A (en) * 1970-05-20 1975-03-11 Xerox Corp Method for electrostatic paper stripping by neutralization of transfer charge
US3851230A (en) * 1972-06-09 1974-11-26 Ricoh Kk Electrostatic transfer-printing sheet stripping device
US3811670A (en) * 1972-06-19 1974-05-21 Xerox Corp Electrostatographic apparatus with air baffle
US3970381A (en) * 1973-02-26 1976-07-20 Xerox Corporation Method and apparatus for xerographic reproduction
US4025180A (en) * 1973-10-30 1977-05-24 Minolta Camera Kabushiki Kaisha Transfer type electrophotographic copying apparatus
US4027960A (en) * 1975-08-06 1977-06-07 Xerox Corporation Transfer system for electrostatic reproduction machine
US4086010A (en) * 1976-11-01 1978-04-25 Xerox Corporation Illumination system utilizing two opposing DC lamps with an optimum barrel-shaped slit
USRE31499E (en) 1976-11-01 1984-01-17 Xerox Corporation Illumination system utilizing two opposing DC lamps with an optimum barrel-shaped slit
US4482240A (en) * 1981-06-24 1984-11-13 Canon Kabushiki Kaisha Electrophotographic process utilizing electrostatic separation and apparatus therefor
US4579441A (en) * 1982-12-03 1986-04-01 Xerox Corporation Detacking apparatus
US4676627A (en) * 1982-12-09 1987-06-30 Canon Kabushiki Kaisha Image forming apparatus
US4640606A (en) * 1983-02-15 1987-02-03 Sharp Kabushiki Kaisha Corona discharger for separating copy paper from photoreceptor in electrophotographic copying machine
US4801975A (en) * 1986-04-18 1989-01-31 Mita Industrial Co. Ltd. Eraser lamp and transparent guide plate in electrostatic image transfer
US4728880A (en) * 1986-11-28 1988-03-01 Eastman Kodak Company Multiple voltage-pulsed corona charging with a single power supply
US5450179A (en) * 1994-02-28 1995-09-12 Eastman Kodak Company Active charging to prevent image disruption
US20040114956A1 (en) * 2002-12-13 2004-06-17 Xerox Corporation Bias charge roller with optimally induced AC corona
US6807389B2 (en) * 2002-12-13 2004-10-19 Xerox Corporation Bias charge roller with optimally induced AC corona

Also Published As

Publication number Publication date
NL6808473A (enrdf_load_stackoverflow) 1968-11-25
FR1568680A (enrdf_load_stackoverflow) 1969-05-23
BE716658A (enrdf_load_stackoverflow) 1968-12-17
GB1242072A (en) 1971-08-11
NL159205B (nl) 1979-01-15
DE1572330B2 (de) 1976-01-22
DE1572330A1 (de) 1970-01-08
CH476332A (de) 1969-07-31
SE338508B (enrdf_load_stackoverflow) 1971-09-06
HK79276A (en) 1976-12-24

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