EP0636951A2 - Zum beidseitigen Bedrucken eines Papierblattes geeigneter elektrophotographischer Drucker - Google Patents

Zum beidseitigen Bedrucken eines Papierblattes geeigneter elektrophotographischer Drucker Download PDF

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Publication number
EP0636951A2
EP0636951A2 EP94111881A EP94111881A EP0636951A2 EP 0636951 A2 EP0636951 A2 EP 0636951A2 EP 94111881 A EP94111881 A EP 94111881A EP 94111881 A EP94111881 A EP 94111881A EP 0636951 A2 EP0636951 A2 EP 0636951A2
Authority
EP
European Patent Office
Prior art keywords
sheet
drum
recording medium
rotating
developing
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Withdrawn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
EP94111881A
Other languages
English (en)
French (fr)
Other versions
EP0636951A3 (de
Inventor
Minoru C/O Nec Corporation Kumagai
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.)
NEC Corp
Original Assignee
NEC Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from JP5208697A external-priority patent/JPH0743959A/ja
Priority claimed from JP5252447A external-priority patent/JPH0784498A/ja
Application filed by NEC Corp filed Critical NEC Corp
Publication of EP0636951A2 publication Critical patent/EP0636951A2/de
Publication of EP0636951A3 publication Critical patent/EP0636951A3/de
Withdrawn legal-status Critical Current

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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
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/28—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which projection is obtained by line scanning
    • G03G15/30—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which projection is obtained by line scanning in which projection is formed on a drum
    • 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
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/23—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 specially adapted for copying both sides of an original or for copying on both sides of a recording or image-receiving material
    • G03G15/231—Arrangements for copying on both sides of a recording or image-receiving material
    • G03G15/232—Arrangements for copying on both sides of a recording or image-receiving material using a single reusable electrographic recording member
    • G03G15/234—Arrangements for copying on both sides of a recording or image-receiving material using a single reusable electrographic recording member by inverting and refeeding the image receiving material with an image on one face to the recording member to transfer a second image on its second face, e.g. by using a duplex tray; Details of duplex trays or inverters

Definitions

  • This invention relates to an electrophotographic pinter which can perform printing on both sides of a sheet of recording medium such as paper.
  • a photosensitive drum having a photoconductive layer on the cylindrical surface rotates on its center axis in a predetermined direction.
  • electrostatic latent images are produced on the photoconductive surface of the rotating drum, and the latent images are developed into visible images with a toner.
  • a sheet of paper is forwarded so as to make contact with the rotating drum at a location where an image transfer means is provided, and the toner images on the drum surface is transferred onto the front side of the paper. After that the transferred images are fixed to the paper by application of heat.
  • the conveyor system for this purpose includes a switchback mechanism which has the advantage of being simple in construction.
  • the switchback mechanism After the operation of the switchback mechanism the retrogressive movement of the paper sheet results in inversion of the head-bottom arrangement of the sheet.
  • the head of the page on the back side is at the back of the bottom of the front page. This is quite inconvenient for fastening similarly printed sheets of paper together.
  • JP 63-54060 A discloses an electrophotographic printer in which the direction of rotation of the photosensitive drum is temporarily reversed at the initial stage of the process of printing on the back side of a sheet of paper after printing on the front side. That is, while the drum is reversely rotated a train of imaging information is supplied to the drum surface until the formation of latent images for one page. During this operation the developing and image transferring treatments are suspended. After that the drum is rotated in the normal direction, and the developing and image transferring treatments are made in the usual way to accomplish printing on the reversed sheet of paper.
  • This printer employs a switchback mechanism to reguide the paper sheet printed on the front side to the transfer unit, permitting inversion of the head-bottom arrangement of the sheet, but the inversion is compensated by the formation of latent images on the reversely rotating drum.
  • a switchback mechanism to reguide the paper sheet printed on the front side to the transfer unit, permitting inversion of the head-bottom arrangement of the sheet, but the inversion is compensated by the formation of latent images on the reversely rotating drum.
  • the printer of JP 63-54060 A is low in printing speed since the development of latent images and the transfer of the developed images to paper are suspended while latent images for one page are formed on the reversely rotating photosensitive drum.
  • it is impossibel to freely reduce the diameter of the drum because the circumference of the drum needs to be longer than the length of the sheet of recording paper so that the drum surface can carry latent images for a full page.
  • the employment of a switchback mechanism for retrogressive conveyance of paper sheets constitutes an obstacle to a reduction in size of the printer because the space necessary for the function of the switchback mechanism depends proportionally on the maximum length of paper sheets used in the printer.
  • the first fixing means is spaced from the transfer means in a first direction which is normal to the center axis of the drum, and the second fixing means is spaced from the transfer means in a second direction opposite to the first direction.
  • the printer further comprises first conveying means for conveying a sheet of recording medium by a sheet forwarding route which extends in the aforementioned first direction to pass through the transfer means and the first fixing means to allow the sheet of recording medium to pass through the transfer means in the first direction while the drum is rotating in the normal direction, second conveying means for conveying a sheet of recording medium by a sheet returning route which starts from an end of the sheet forwarding route, turns so as to reverse the sheet of recording medium under conveyance and then extends in the second direction to the transfer means to allow the reversed sheet of recording medium to pass through the transfer means in the second direction while the drum is rotating in the reverse direction, and a delivery passageway which extends from the transfer means in the second direction and passes through the second fixing means.
  • the printer according to the invention has two oppositely arranged fixing means, one for printing on the front side of a sheet of recording medium (usually paper) and the other for printing on the back side of the same sheet.
  • the sheet After performing printing on the front side of the sheet by using the first developing means and the first fixing means, the sheet is returned to the transfer means by the sheet returning route which is curved so as to reverse the sheet and reverse the direction of movement of the sheet without using any switchback mechanism. Therefore, the forward edge of the moving sheet remains unchanged.
  • the direction of rotation of the photosensitive drum is reversed before forming images to be printed on the back side of the sheet (upper side of the reversed sheet), and this is accompanied by the switchover of the first developing means to the second developing means. Therefore, the head-bottom arrangement of the images printed on the back side of the sheet conforms with that on the front side.
  • Fig. 1 shows an electrophotographic printer as an embodiment of the invention.
  • the printer includes a paper cassette 12 containing a neat stack of some sheets of recording paper 10.
  • the paper sheets 10 can be drawn out one by one by a takeout roller 14.
  • the principal element of the printer is a photosensitive drum 20 which has a photoconductive layer 20a on the cylindrical surface.
  • the drum 20 can be rotated on its center axis C which extends horizontally. Normally the drum 20 is rotated in the direction of arrow N, but according to the need the drum 20 can be rotated in the reverse direction indicated by arrow R.
  • a paper forwarding route 16 extends from the takeout roller 14 to the position of the transfer unit 40 to bring a sheet of paper into contact with the drum surface 20a right above the transfer unit 40. From the paper outlet 40a of the transfer unit 40 the paper forwarding route 16 further extends to a first fixing unit 50A. There is a paper conveying means 18 to convey each sheet of paper by the forwarding route 16.
  • the paper forwarding route 16 turns upward and connects with a paper returning route 60 which turns downward and extends to the paper outlet 40a of the image transfer unit 40.
  • a paper returning route 60 which turns downward and extends to the paper outlet 40a of the image transfer unit 40.
  • the paper returning route 60 is used to perform printing on both sides of a sheet of paper.
  • the end part of the forwarding route 16 and the returning route 60 are curved such that the paper sheet makes a 180-degree turn across a horizontal plane, and as a result the paper sheet is reversed before it is returned to the transfer unit 40. In this printer the paper sheet makes no retrogressive movement.
  • a switching guide 66 When it suffices to make printing on one side of a paper sheet, a switching guide 66 is moved into an open position (as shown in solid line in Fig. 1) to break the returning route 60 and allow the paper sheet to be passed to an intermediary delivery tray 70 by a guide roller 64.
  • a paper sensor 68 is provided to the returning route 60 at a location downstream from the switching guide 66 to detect the passage of a paper sheet at that location.
  • the distance from the transfer unit 40 to the position of the paper sensor 68 is made longer than the maximum length of paper sheets 10 to be used in this printer in order to accomplish reversing of every paper sheet.
  • the photosensitive drum 20 is disposed in a central section.
  • the top face of the casing 24 is formed with a slit 26 which is parallel to the center axis C of the drum 20, and the exposure unit 30 is arranged so as to project a laser beam onto the cylindrical, photoconductive surface 20a of the drum 20 through the slit 26.
  • a first charger 28A and a first developing means 32A are arranged against the cylindrical surface of the drum 20 at a suitable angular distance.
  • the toner 36 adheres to the drum surface 20a only in the areas of the electrostatic latent images where negative charges are absent, whereby the latent images are developed into visible toner images.
  • the developing sleeve 42 is retractable so as to stay detached from the drum 20.
  • the bottom of the casing 24 is formed with a slit 44 by which the cylindrical surface 20a of the drum 20 is locally exposed. Therefore, the paper sheet 10 makes contact with the surface 20a of the rotating drum 20. From the back side of the paper 10 the transfer unit 40 applies positive charges to the drum surface 20a to transfer the toner images from the drum surface to the paper.
  • the cleaning means 46A includes a cleaning brush 48 for removing residual toner from the drum surface 20a and a discharging lamp 52 for dissipation of residual electric charges from the drum surface 20a.
  • the brush 48 is pivoted to an inner part of the casing 24 and can be held either in contact with the drum surface 20a or detached from the drum.
  • the lamp 52 is located outside the casing 24 and projects light onto the drum surface 20a through a slit 54 in the casing 24.
  • the image setting unit 22 has a second charger 28B and a second developing means 32B.
  • the first and second chargers 28A and 28B are arranged symmetrical, and the first and second developing means 32A and 32B are arranged symmetrical.
  • the second charger 28B has the same function as the first charger 28A.
  • the second developing means 32B is identical with the first developing means 32A in construction and function.
  • the second developing means 32B has a toner container 34 containing a toner 36, a stirring paddle 38 and a developing sleeve 42.
  • a second cleaning means 46B which includes a cleaning brush 48 and a discharging lamp 52 similarly to the first cleaning means 46A.
  • a memory means for temporary storage of information for producing latent images
  • a memory means with a capacity sufficient to store information for both sides of a paper sheet as a precaution against accidental interruption of the printing process at the last stage of making printing on the back side.
  • the photosensitive drum 20 For printing on the front side of a paper sheet 10 the photosensitive drum 20 is rotated in the direction of arrow N, and the paper sheet is forwarded in the direction of arrow F toward the transfer unit 40 while the switching guide 76 takes the position A in Fig. 2.
  • the discharging lamp 52 of the first cleaning means 46A is operated to remove residual electric charges from the photoconductive surface 20a of the drum 20, and then the first charger 28A is operated to negatively charge the drum surface 20a.
  • the exposure unit 30 is operated to produce electrostatic latent images on the drum surface 20a while the first developing means 32A is operated to develop the latent images with the toner 36, and the developed images are transferred to the front side of the paper sheet 10 by the operation of the transfer unit 40.
  • the paper sheet is passed to the first fixing unit 50A to heat fix the images on the front side of the paper sheet.
  • the paper sheet follows the paper returning route 60 while the switching guide 66 is in the closed position.
  • the paper sheet moving in the direction of arrow B, returns to the transfer unit 40 the paper sheet is already reversed. That is, the upper side of the paper sheet moving in the direction B is the back side of the sheet.
  • Printing on the paper sheet moving in the direction B is performed in the following way.
  • a controller (not shown) of the printer commands the photosensitive drum 20 to rotate in the reverse direction indicated by arrow R.
  • the second charger 28B, the second developing means 32B and the second cleaning means 46B begin to operate.
  • the discharging lamp 52 of the second cleaning means 46B is used to remove residual electric charges from the surface 20a of the drum 20, and the second charger 28B is used to negatively charge the drum surface 20a.
  • the exposure unit 30 is operated to produce electrostatic latent images on the drum surface 20a while the second developing means 32B is operated to develop the latent images with the toner 36, and the developed images are transferred to the back side (now upper side) of the paper sheet 10 by the operation of the transfer unit 40.
  • the switching guide 76 is in the position B in Fig. 2 in order to pass the paper sheet from the transfer unit 40 to the second fixing unit 50B by the paper delivery passageway 74.
  • the images on the back side of the paper sheet are heat fixed by the second fixing unit 50B, and the paper sheet is ejected into the delivery tray 80.
  • the direction of movement of the paper sheet is reversed, and the direction of rotation of the photosensitive drum 20 is also reversed, and the reversing is accompanied by the switchover of the first set of charger 28A, developing means 32A and cleaning means 46A to the oppositely arranged second set of charger 28B, developing means 32B and cleaning means 46B. Therefore, the head-bottom arrangement of the printed images on the back side of the paper conforms with that on the front side.
  • the printing time required for each sheet of paper can be shortened because in printing on each side of the paper the formation of latent images, development of the latent images and the transfer of the developed images can be performed continuously.
  • the printer can be made relatively small in size because the diameter of the photosensitive drum 20 can be reduced and also because the total length of the paper forwarding and returning routes necessary for reversing the paper sheet is relatively short.
EP94111881A 1993-07-30 1994-07-29 Zum beidseitigen Bedrucken eines Papierblattes geeigneter elektrophotographischer Drucker. Withdrawn EP0636951A3 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP5208697A JPH0743959A (ja) 1993-07-30 1993-07-30 電子写真プリンタ
JP208697/93 1993-07-30
JP5252447A JPH0784498A (ja) 1993-09-14 1993-09-14 画像形成装置
JP252447/93 1993-09-14

Publications (2)

Publication Number Publication Date
EP0636951A2 true EP0636951A2 (de) 1995-02-01
EP0636951A3 EP0636951A3 (de) 1995-09-20

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP94111881A Withdrawn EP0636951A3 (de) 1993-07-30 1994-07-29 Zum beidseitigen Bedrucken eines Papierblattes geeigneter elektrophotographischer Drucker.

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EP (1) EP0636951A3 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7179002B2 (en) 2003-12-31 2007-02-20 Samsung Electronics Co., Ltd. Thermal image forming apparatus
CN104249549A (zh) * 2013-06-28 2014-12-31 株式会社宫腰 电子照相方式正反两面印刷单张纸印刷机

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5622455A (en) * 1979-07-31 1981-03-03 Ricoh Co Ltd Reciprocating reader
GB1590872A (en) * 1978-05-31 1981-06-10 Xerox Corp Electrostatographic apparatus
EP0476921A2 (de) * 1990-09-18 1992-03-25 Mita Industrial Co. Ltd. Bilderzeugungsgerät
DE4204470A1 (de) * 1991-02-15 1992-08-20 Toshiba Kawasaki Kk Elektrostatographisches geraet
JPH0588588A (ja) * 1991-09-26 1993-04-09 Ricoh Co Ltd 合成画像形成方法及び装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1590872A (en) * 1978-05-31 1981-06-10 Xerox Corp Electrostatographic apparatus
JPS5622455A (en) * 1979-07-31 1981-03-03 Ricoh Co Ltd Reciprocating reader
EP0476921A2 (de) * 1990-09-18 1992-03-25 Mita Industrial Co. Ltd. Bilderzeugungsgerät
DE4204470A1 (de) * 1991-02-15 1992-08-20 Toshiba Kawasaki Kk Elektrostatographisches geraet
JPH0588588A (ja) * 1991-09-26 1993-04-09 Ricoh Co Ltd 合成画像形成方法及び装置

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 17, no. 432 (P-1589) 10 August 1993 & JP-A-05 088 588 (RICOH) 9 April 1993 *
PATENT ABSTRACTS OF JAPAN vol. 5, no. 73 (P-061) 15 May 1981 & JP-A-56 022 455 (RICOH) 3 March 1981 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7179002B2 (en) 2003-12-31 2007-02-20 Samsung Electronics Co., Ltd. Thermal image forming apparatus
CN104249549A (zh) * 2013-06-28 2014-12-31 株式会社宫腰 电子照相方式正反两面印刷单张纸印刷机
EP2818935A1 (de) * 2013-06-28 2014-12-31 Miyakoshi Printing Machinery Co., Ltd. Elektrofotografische Vorder- und Rückseitendruckmaschine mit Blattzuführung
US9207618B2 (en) 2013-06-28 2015-12-08 Miyakoshi Printing Machinery Co., Ltd. Electrophotographic sheet-fed front/back printing machine
CN104249549B (zh) * 2013-06-28 2018-02-23 株式会社宫腰 电子照相方式正反两面印刷单张纸印刷机

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Publication number Publication date
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