US3866573A - Electrostatic copying apparatus - Google Patents

Electrostatic copying apparatus Download PDF

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Publication number
US3866573A
US3866573A US300379A US30037972A US3866573A US 3866573 A US3866573 A US 3866573A US 300379 A US300379 A US 300379A US 30037972 A US30037972 A US 30037972A US 3866573 A US3866573 A US 3866573A
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United States
Prior art keywords
layer
combination
cylindrical portion
dielectric layer
roller
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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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US300379A
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English (en)
Inventor
Roland Szostak
Guenther Maurischat
Ulrich Krekeler
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Agfa Gevaert AG
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Agfa Gevaert AG
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/14—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
    • G03G15/1665—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 by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat
    • G03G15/167—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 by introducing the second base in the nip formed by the recording member and at least one transfer member, e.g. in combination with bias or heat at least one of the recording member or the transfer member being rotatable during the transfer

Definitions

  • the roller has a dielectric elastic outer cylindrical layer having a thickness of 0.020.5 millimeter, a hardness of 30-60 Shore and consisting of a polyolefine; an inner elastic cylindrical layer having a thickness of 2l() millimeters and consisting of a polyurethane; a deformable third cylindrical layer galvanized onto the inner elastic layer, surrounded by the outer elastic layer, consisting of gold, copper, cadmium or tin and having a thickness of 0.02-2 microns; and a hollow metallic corewhich is surrounded by the inner elastic layer and is elastically connected with the third layer.
  • the outer elastic layer is charged by the positive electrode of a corona discharge device which 19 Claims, 4 Drawing Figures PATENIEDFEBWIHYS I 3 866 573 SHEET 1 OF 2 Fig.2 m j ELECTROSTATIC COPYING APPARATUS CROSS-REFERENCE TO RELATED APPLICATION
  • Certain features of the electrostatic copying apparatus of the present invention are disclosed and claimed in the commonly owned copending application Ser. No. 300,376 filed by Szostak and Kruger on Oct. 24, 1972 and entitled Electrostatic copying apparatus with means for preventing contamination of transfer material.
  • the present invention relates to electrostatic copying apparatus in general, and more particularly to improvements in electrostatic copying apparatus of the type wherein the rear side of a sheet consisting of transfer material is biased by a preferably roller-shaped countersurface in order to maintain the front side of the sheet in contact with a mobile xerographic surface during transfer of powder images.
  • the countersurface comprises a dielectric outer layer to effect the transfer of pulverulent material from the electrostatically charged xerographic surface during engagement of the xerographic surface with the adjacent surface of a sheet which is biased by the countersurface.
  • the charging of dielectric layer of the countersurface is effected by a corona discharge device.
  • a drawback of presently known electrostatic copying apparatus of the just outlined character is that the material of the countersurface is too rigid so that the dielectric layer of the countersurface cannot insure a satisfactory transfer of powder images. This is due to the fact that the dielectric layer surrounds a metallic electrode of the countersurface and is incapable of yielding so as to closely follow the outline of that portion .of a sheet which is in the process of receiving a powder image or to closely follow the outline of that portion of the xerographic surface which is in the process of being relieved of the powder image. It was already proposed to provide the dielectric layer of the countersurface with an inhomogeneous charge so as to enhance its effect upon the particles of the powder image.
  • the dielectric layer of such apparatus must be provided with a substantial charge because at least some portions of the charge are often located at a considerable distance from the powder image.
  • An object of the invention is to provide an electrostatic copying apparatus with a novel and improved countersurface which can insure satisfactory transfer of powder images onto sheets of transfer material and which can insure a satisfactory image transfer even if the configuration of the xerographic surface deviates from an optimum configuration.
  • Another object of the invention is to provide an electrostatic copying apparatus which embodies the improved countersurface.
  • a further object of the invention is to provide a mum tersurface whose dielectric layer need not be charged to the extent which is necessary in certain presently known electrostatic copying apparatus.
  • An additional object of the invention is to provide novel and improved means for charging the dielectric layer of the countersurface in an electrostatic copying apparatus.
  • Still another object of the invention is to provide a deformable countersurface.
  • An ancillary object of the invention is to provide a countersurface which can be used in existing electrostatic copying apparatus and whose mounting in existing apparatus necessitates relatively minor changes in the design of such apparatus.
  • the improved electrostatic copying apparatus comprises transporting means which serves to advance a series of discrete sheets of transfer material along a predetermined path toward, through and beyond a transfer station, an electrostatically charged xerographic surface located at one side of the path and arranged to transport powder images toward the transfer station, and a countersurface which is located at the other side of the path and serves to maintain the xerographic surface in contact with sheets advancing through the transfer station.
  • the countersurface comprises a preferably cylindrical sheet-contacting outer layer which consists of elastomeric material and may have a thickness of 002-05 millimeter and a hardness of 3060 Shore, a relatively thin preferably cylindrical currentconducting second layer which may consist of gold, copper, cadmium or tin and may have a thickness of 0.02-2 microns, and a relatively thick preferably cylindrical third layer consisting of elastomeric material and preferably having a thickness of 2-10 millimeters.
  • the second layer surrounds the third layer and is surrounded by the first layer
  • the countersurface preferably further comprises a tubular metallic core which is surrounded by the third layer and is electrically connected with the second layer by way of an extension of the second layer which preferably overlies one or both axial ends of the third layer.
  • the first layer can be charged by the positive electrode of a corona discharge device which is in circuit with a source of high-voltage current. One pole of the current source is connected with the second layer by way of the metallic core.
  • FIG. I is a fragmentary vertical sectional view of an electrostatic copying apparatus employing a countersurface which embodies tthe invention
  • FIG. 2 is a sectional view as seen in the direction of arrows from the line Il-Il of FIG. 1;
  • FIG. 3 is a fragmentary axial sectional view of the countersurface, illustrating the charging of the dielectric layer
  • FIG. 4 is a fragmentary diagrammatic sectional view of the xerographic surface and the countersurface, showing the transfer of a powder image onto a sheet of transfer material.
  • FIGS. 1 and 2 there is shown a portion of an electrostatic copying apparatus which comprises a frame 2 supporting a horizontal shaft l for a carrier structure including a pair of two-armed levers 3 and 4.
  • the longer arms of the levers 3, 4 support a second horizontal shaft 5 which in turn supports a freely rotatable countersurface here shown as an idler roller 106.
  • the roller 106 comprises a tubular metallic core 6 which is rotatable with the outer races of antifriction bearings 5a (only one shown in FIG. 2) provided on the shaft 5 between the carrier levers 3 and 4.
  • the peripheral surface of the core 6 is surrounded by a cylindrical portion or layer 7 which consists of elastomeric material and is somewhat shorter than the core 6.
  • the layer 7 may consist of a polyurethane with a hardness of 3060 Shore.
  • the elastomeric layer 7 is surrounded by a much thinner metallic cylindrical portion or layer 8 which is preferably galvanized onto the peripheral surface of the layer 7 and is in turn surrounded by a dielectric outer elastomeric cylindrical portion or layer 9.
  • the right-hand axial end of the currentconducting layer 8 is provided with an inwardly extending portion or extension 8a which overlies the respective axial end of the elastomeric layer 7 and has a smaller diameter neck portion 8b which is electrically connected with the metallic core 6.
  • a similar extension can be provided at the other axial end of the layer 8 to overlie the left hand exial end of the layer 7 and to contact the core 6.
  • the metallic layer 8 onto the elastomeric layer 7 is preferably coated with a binder or bonding agent, such as Silane.
  • a binder or bonding agent such as Silane.
  • a coat of reduction silver is sprayed over it to form a conductive layer which is sufficient for subsequent galvanic deposition of a ductile metal, such as gold, copper, cadmium or tin, which is to form the current-conducting layer 8.
  • a ductile metal such as gold, copper, cadmium or tin
  • the minimum thickness of the layer 8 is preferably not less than 0.02 micron in order to insure that this layer forms an uninterrupted coat around the entire elastic layer 7.
  • the maximum thickness of the layer 8 preferably does not exceed 2 microns so as not to overly stiffen the elastomeric inner layer 7.
  • the dielectric layer 9 can constitute an elastic pipe or hose which is shrunk onto the metallic layer 8 and has a dielectric constant 2-6.
  • the shorter arms of the levers 3, 4 are connected to each other by a rod 10a which is articulately coupled to the reciprocable armature 10 of an electromagnet 11.
  • the electromagnet 11 When the electromagnet 11 is energized, the armature l0 pivots the levers 3, 4 against the opposition of one or more helical springs 12 which tend to maintain the levers 3, 4 in abutment with fixed stops 15, 16.
  • the roller 106 then assumes the operative position of FIG. 1 in which its outermost layer 9 bears against the un derside of a sheet 19 of transfer material.
  • the region of contact between the sheet 19 and the layer 9 is located at a transfer station TS where the upper side of the sheet 19 receives a powder image PI from (the) se
  • the path for transport of successive sheets 19 toward, through and beyond the transfer station TS is defined by two guides 17, 18. It will be noted that such path extends between the roller 106 and the xero graphic surface 14.
  • the guides 17, 18 can be said to form part of a transporting mechanism which advances a series of sheets 19 in the direction indicated by arrow A and may include, for example, a roller which removes successive sheets from a stack located to the left of the guide 17, as viewed in FIG. 1.
  • a transporting mechanism which advances a series of sheets 19 in the direction indicated by arrow A
  • the guide 17 is formed with an opening 17a for a portion of a scanning device 20 arranged to close a microswitch 21 in response to detection of the leading portion of a sheet 19 and to open the switch 21 when the trailing portion of a sheet 19 on the guide 17 advances beyond the opening 170.
  • the switch 21 controls a time-delay device 22 which energizes the electromagnet 11 when the leading portion of a sheet 19 reaches the transfer station TS and deenergizes the electromagnet 11 when the trailing portion of a sheet 19 reaches or moves only slightly beyond the transfer station.
  • the details of the time-delay device 22 and its mode of operation are described in the aforementioned copending application Ser. No. 300,376 filed Oct. 24, 1972 by SZOSTAK et al. and entitled Electrostatic copying apparatus with means for preventing contamination of transfer material.
  • the timedelay device 22 is connected in the circuit 23, 24 of the electromagnet 11.
  • the means for charging the dielectric layer 9 of the roller 106 comprises a corona discharge device having a wirelike positive electrode 25 and a grounded housing 26.
  • the electrode 25 is connected with a source 27 of high-voltage energy.
  • the charging circuit is completed by connecting the metallic layer 8 with a grounded conductor 28 (i.e., with one pole of the energy source 27) by way of the shaft 1, levers 3, 4 core 6 and extension 8a, 8b.
  • the xerographic surface 14 is connected to the ground by way of an elastic contact 29 or the like.
  • FIGS. 3 and 4 respectively illustrate the field lines during charging of the dielectric layer 9 on the roller 106 and during transfer of a powder image PI onto a sheet 19.
  • the field lines of charge particles which are sprayed by the positive electrode 25 onto the dielectric layer 9 are tied primarily to negative charge particles in the metallic layer 8. Consequently, such lines cannot interfere with further spraying of charge particles and cannot adversely influence each other. This insures that, even at low charging voltages, the dielectric layer 9 is provided with a dense and uniform charge.
  • the elasticity of the layers 7, 9 and the flexibility or deformability of the layer 8 insures that the layer 9 can closely follow the outline of the selenium layer 13 at the transfer station TS. This guarantees an optimum utilization of the charge of the dielectric layer 9. Moreover, the elasticity of the roller 106 reduces the likelihood of damage to the sensitive surface of the selenium layer 13.
  • the layer 9 can exhibit a relatively low elasticity, i.e., its thickness can be minimal (0.02 0.5 millimeter). Consequently, the exposed surface of the layer 9 is closely adjacent to the metallic layer 8 so that the layer 9 can store a substantial charge of great uniformity by the application of relatively low charging voltages. This can be explained as follows: The fields of the charge particles at the exposed surface of the thin dielectric layer 9 are strongly attracted to the metallic layer 8 and thus cannot interfere with further charging and/or with the fields of the adjacent charge particles. It was further found that the metallic layer 8 can be made so thin that it does not interfere with elastic deformation of the layers 7, 9 and is not damaged during deformation of such elastomeric layers.
  • the hollow core 6 contributes to lower weight and lower inertia of the roller 106. This is desirable in order to insure that the powder image to be transferred is not blurred during initial contact of the layer 9 with a shee 19 at the transfer station.
  • the provision of bearings 5a also contributes to a reduction of friction between the roller 106 and its carrier structure. However, it is also possible to utilize a roller 106 which is driven at the exact speed of movement of sheets 19 along the path defined by the guides 17 and 18.
  • the thickness of the elastomeric layer 7 may be in the range of 2-10 millimeters.
  • the material of the layer 9 may be a polyolefine, preferably polyethylene, or a halogenated polyolefine, preferably polyvinyl chloride.
  • the material of the dielectric layer 9 preferably exhibits a high zone resistance and a smooth external surface with a high surface resistance preferably exceeding (1. Moreover, the layer 9 should exhibit a high resistance to puncturing and should be sufficiently stiff, in spite of its minimal wall thickness, to avoid a distortion of the transferred image even though the elasticity of the layer 7 is preferably high.
  • the aforementioned metals (gold, copper, cadmium and tin) were found to be particularly suited for galvanic deposition of the layer 8. They are good conduc tors of electric current even when the thickness of the layer 8 is only a small fraction of 1 micron and are resistant to ozone. Moreover, such materials are pliable so that they can readily follow the outline of the elastically deformed layer 7 and/or 9 without undergoing permanent deformation.
  • the combination of transporting means arranged to advance a series of sheets of transfer material along a predetermined path toward, through and beyond a transfer station; an electrostatically charged xerographic surface located at one side of said path and arranged to transport powder images toward said transfer station; and a countersurface located at the opposite side of said path and arranged to maintain said xerographic surface in image-receiving contact with sheets advancing through said transfer station, said countersurface including a relatively thin sheet-contacting dielectric layer consisting of elastomeric material, a relatively thin currentconducting flexible second layer, and a relatively thick third layer consisting of elastomeric material, said second layer being disposed between said dielectric layer and said third layer.
  • said countersurface comprises a roller having a first cylindrical portion constituting said dielectric layer, a second cylindrical portion constituting said second layer, and a third cylindrical portion constituting said third layer, said first and second cylindrical portions respectively surrounding said second and third cylindrical portions.
  • roller further comprises a core consisting at least in part of current-conducting material and surrounded by said third cylindrical portion.
  • said second layer is a metal selected from the group consisting of gold, copper, cadmium and tin,
  • the combination of transporting means arranged to advance a series of sheets of transfer material along a predetermined path toward, through and beyond a transfer station; an electrostatically charged xerographic surface located at one side of said path and arranged to trans port powder images toward said transfer station; and a countersurface comprising a roller located at the op' postie side of said path and arranged to maintain said xerographic surface in contact with sheets advancing through said transfer station, said roller having a rela tively thin sheet-contacting first cylindrical portion constituting a dielectric layer and consisting of elastomeric material, a relatively thin flexible second cylindrical portion constituting a current-conducting second layer, and a relatively thick third cylindrical portion constituting a third layer and consisting of elastomeric material, said first and second cylindrical portions respectively surrounding said second and third cylindrical portions, and said roller further comprising a core consisting at least in part of current-conducting material and being surrounded by said third cylindrical portion, said third cylindrical portion having an axial

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
US300379A 1971-10-21 1972-10-24 Electrostatic copying apparatus Expired - Lifetime US3866573A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2152501A DE2152501B2 (de) 1971-10-21 1971-10-21 Vorrichtung zur Übertragung von pulverformigen Tonerbildern

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4099487A (en) * 1975-06-10 1978-07-11 Agfa-Gevaert N.V. Roller with adjustable length
US5168313A (en) * 1988-04-28 1992-12-01 Kabushiki Kaisha Toshiba Toner image transfer method and device for electrophotographic printing apparatus
WO1992022430A1 (en) * 1991-06-10 1992-12-23 Sinvent A/S A method and a system for layer-wise and pattern-wise controlled application of particulate material onto a receiving unit
EP0775947A1 (de) * 1995-12-07 1997-05-28 COMPUPRINT S.p.A. Elektrophotographisches Druckgerät mit einer mittels einer Korona polarisierten Übertragungsrolle
US20070212125A1 (en) * 2006-03-08 2007-09-13 Konica Minolta Business Technologies, Inc. Image forming apparatus and image forming method
US20080226321A1 (en) * 2007-03-13 2008-09-18 Akitomo Kuwabara Image forming apparatus and tandem image forming apparatus
US20090010667A1 (en) * 2007-07-05 2009-01-08 Hiroyuki Mabuchi Transfer apparatus, transfer method, and image forming apparatus
US9798272B2 (en) * 2016-03-16 2017-10-24 Fuji Xerox Co., Ltd. Image forming apparatus

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2807233A (en) * 1954-03-29 1957-09-24 Ibm Electrophotographic printing machine
US3449548A (en) * 1966-12-30 1969-06-10 Xerox Corp Fusing device
US3626260A (en) * 1968-03-19 1971-12-07 Iwatsu Electric Co Ltd Method and apparatus for applying voltage in electrophotography
US3633543A (en) * 1969-12-05 1972-01-11 Xerox Corp Biased electrode transfer apparatus
US3672884A (en) * 1968-10-14 1972-06-27 Xerox Corp Electrostatic printing and developing
US3691993A (en) * 1970-11-23 1972-09-19 Ibm Apparatus for transferring developed image

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2807233A (en) * 1954-03-29 1957-09-24 Ibm Electrophotographic printing machine
US3449548A (en) * 1966-12-30 1969-06-10 Xerox Corp Fusing device
US3626260A (en) * 1968-03-19 1971-12-07 Iwatsu Electric Co Ltd Method and apparatus for applying voltage in electrophotography
US3672884A (en) * 1968-10-14 1972-06-27 Xerox Corp Electrostatic printing and developing
US3633543A (en) * 1969-12-05 1972-01-11 Xerox Corp Biased electrode transfer apparatus
US3691993A (en) * 1970-11-23 1972-09-19 Ibm Apparatus for transferring developed image

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4099487A (en) * 1975-06-10 1978-07-11 Agfa-Gevaert N.V. Roller with adjustable length
US5168313A (en) * 1988-04-28 1992-12-01 Kabushiki Kaisha Toshiba Toner image transfer method and device for electrophotographic printing apparatus
WO1992022430A1 (en) * 1991-06-10 1992-12-23 Sinvent A/S A method and a system for layer-wise and pattern-wise controlled application of particulate material onto a receiving unit
EP0775947A1 (de) * 1995-12-07 1997-05-28 COMPUPRINT S.p.A. Elektrophotographisches Druckgerät mit einer mittels einer Korona polarisierten Übertragungsrolle
US20070212125A1 (en) * 2006-03-08 2007-09-13 Konica Minolta Business Technologies, Inc. Image forming apparatus and image forming method
US7558497B2 (en) * 2006-03-08 2009-07-07 Konica Minolta Business Technologies, Inc. Image forming apparatus and image forming method
US20080226321A1 (en) * 2007-03-13 2008-09-18 Akitomo Kuwabara Image forming apparatus and tandem image forming apparatus
US7953335B2 (en) 2007-03-13 2011-05-31 Ricoh Company, Ltd. Image forming apparatus and tandem image forming apparatus
US20090010667A1 (en) * 2007-07-05 2009-01-08 Hiroyuki Mabuchi Transfer apparatus, transfer method, and image forming apparatus
US7970307B2 (en) 2007-07-05 2011-06-28 Ricoh Company, Ltd. Methods and apparatus for transferring a toner image via electrophotographics
US9798272B2 (en) * 2016-03-16 2017-10-24 Fuji Xerox Co., Ltd. Image forming apparatus

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Publication number Publication date
DE2152501B2 (de) 1980-02-14
DE2152501A1 (de) 1973-04-26

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