US3921571A - Multiple development method and apparatus for electrophotographic copiers - Google Patents

Multiple development method and apparatus for electrophotographic copiers Download PDF

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Publication number
US3921571A
US3921571A US482040A US48204074A US3921571A US 3921571 A US3921571 A US 3921571A US 482040 A US482040 A US 482040A US 48204074 A US48204074 A US 48204074A US 3921571 A US3921571 A US 3921571A
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US
United States
Prior art keywords
support medium
image
developer
development
latent electrostatic
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
Application number
US482040A
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English (en)
Inventor
Robert A Moore
Daniel J Sullivan
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.)
Ricoh Co Ltd
Original Assignee
Itek 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
Application filed by Itek Corp filed Critical Itek Corp
Priority to US482040A priority Critical patent/US3921571A/en
Priority to CA225,258A priority patent/CA1058980A/en
Priority to GB16750/75A priority patent/GB1495429A/en
Priority to NL7507130A priority patent/NL7507130A/xx
Priority to FR7519177A priority patent/FR2276617A1/fr
Priority to IT24613/75A priority patent/IT1039178B/it
Priority to AU82348/75A priority patent/AU496269B2/en
Priority to SE7507188A priority patent/SE407118B/xx
Priority to DE2528109A priority patent/DE2528109C2/de
Priority to JP50077095A priority patent/JPS5118548A/ja
Priority to BE157634A priority patent/BE830585A/xx
Application granted granted Critical
Publication of US3921571A publication Critical patent/US3921571A/en
Assigned to RICOH COMPANY, LTD. reassignment RICOH COMPANY, LTD. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: ITEK CORPORATION
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0801—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer for cascading

Definitions

  • ties is preferably accomplished by significantly reducing the width of the gap between the latent image bearing medium and the development plate through which the developer falls. This increases the density of References Cited UNITED STATES PATENTS developer in the gap and the degree of developer agi- 118/637 tation and, hence, causes it to fall much slower while 118/6 still ensuring an adequate supply for effective develop- H3/637 ment of all areas of the image. With a system designed in this way copies having a quality equal or Superior to those obtainable with conventional systems can be 3,592,642 3,736,055 Davidge et al..
  • the present invention relates generally to the field of electrophotographic copiers, and, more particularly, to an electrophotographic copier having a multiple development capability for improving the quality of images containing extended solid and half-tone areas.
  • Another approach is to leave the size of the developing station alone, but instead cause the latent image to move through it at a slower speed. This is also unsatisfactory because it requires that other operations of the machine be accelerated or adjusted to maintain high overall operating speed and this makes the machine more complex and less reliable.
  • the above inadequacies have been significantly reduced by providing an electrophotographic copying system having a multiple development capability which may be utilized in a selective manner to more fully develop those latent images 5 which contain extended solid areas. More particularly,
  • the present invention permits the latent image to be directed through the development station a plurality of times as needed or desired to ensure that high density black images of pictures, graphs or the like can be produced.
  • This multiple development capability is attained by the provision of a development station of novel construction which avoids any significant image degradation that would normally be expected to occur as a result of the image passing through the development station more than one time.
  • multiple development would actually tend to damage the developed (or partially developed) image more than enhance it, because as the image is passed through the development station for a second or subsequent time, there would be a substantial tendency for the carrier beads to physically rub against and noticeably damage background areas by producing a high density of black spots thereon, and, also, to cause edges of the image to become less well defined.
  • the developing station has been designed such that the developer and the latent electrostatic image can be moved through it at substantially identical speeds such that there will not be any significant scrubbing or wiping action between them, and because there is no significant scrubbing, there will be no significant image degradation during second and subsequent development operations.
  • the spacing or gap between the drum that carries the latent electrostatic image and the development plate or electrode is reduced significantly. This reduced spacing results in a higher particle density and a higher frequency of developer collisions in the gap and, hence, in a slower movement of the developer through the gap. Also, this increased density will ensure that a large amount of developer be present adjacent each area of the image to be developed to ensure full development.
  • the development electrode is preferably designed with a knurled surface in the manner disclosed in copending U.S.
  • Such an electrode design permits a better and more uniform spreading of the developer to be effected to further ensure that sufficient toner will be available to all areas of the image.
  • the system provided permits multiple development to be selectively utilized in those situations when needed or desired to completely develop an image such as when the original contains extended solid areas.
  • multiple development is not needed, such as when the original contains only line copy or when improved image quality is not important, only a single development need be performed without any loss in copy speed.
  • FIGURE schematically illustrates the development station of an electrophotographic copier in accordance with a presently preferred embodiment of the invention.
  • FIGURE illustrates, in somewhat schematic form, the development area of an electrophotographic copier.
  • Other conventional portions of the copier such as the imaging station, the corona charging station, the exposure station and the drum cleaning station have not been shown in the interest of clarity and because they do not form a part of the present invention.
  • reference number 1 identifies the photoconductive drum upon the surface of which a latent electrostatic image has been formed in the conventional manner.
  • Reference number 2 identifies the developer supply hopper while reference numbeer 3 refers to the development plate or electrode which is spaced from the surface of drum 1 to define a gap or space 4 therebetween as understood by those skilled in the art.
  • developer is dispensed from developer hopper 2 and cascades downwardly through the gap 4 such that toner will be attracted to the latent electrostatic image on the surface of drum 1 being carried through the development station in the direction indicated by arrow 5.
  • the developer thereafter falls to the bottom of the machine where it is usually replenished with fresh toner and is picked up by conveyer 6 controlled by a motor 10 which carries it back to the top of the machine to be recirculated therethrough.
  • belt 8 is adapted to be carried across the drum in the direction indicated by arrow 7 by a suitable roller system 9, 11 and can be selectively brought into or out of contact with the drum by means of a spring roller 12 or the like as will be explained in greater detail hereinafter.
  • Belt 8 and its associated structure does not form part of the present invention, and is illustrated schematically only to help explain the invention. It should be clearly understood, however, that the present invention could also be employed in those systems wherein an image is transferred directly from the photoconductive drum to paper or to other mediums using electrostatic transfer.
  • Development plate 3 functions as a metallic electrode and is thus electrically connected to a conventional bias source 13 as is well recognized by those skilled in the art.
  • development electrode 3 is provided with a knurled surface of the type described in the earlier-mentioned copending US. Patent Application Ser. No. 429,616 which assists in distributing the developer more uniformly over the entire image to be developed.
  • gap 4 formed between the surface of drum 1 and plate 3 is designed to be substantially narrower than those employed in conventional systems.
  • gap 4 has a spacing of approximately 175 mils in region 16, a spacing of about mils in region 17, a spacing of about 85 mils in re gion 18 and a spacing of about mils in region 19. This variable spacing has been provided to ensure a rel atively smooth flow of developer into and out of gap 4 without creating excessive pile-ups while maintaining the very narrow spacing desired in the longer central region of the gap.
  • spacings both variable and uniform may also be employed if desired, however, and, as a general rule, a spacing of from about 50 mils to about 300 mils with central areas of the gap preferably being less than about lOO mils would satisfy the requirements of the present invention and permit multiple development.
  • the toner mixture itself is of conventional type consisting of carrier beads having toner powder adhered thereto and having an average diameter of about 15 mils. Obviously, for different sized beads, somewhat different gap widths might be employed.
  • the electrophotographic copier will, in only a single development cycle, produce copies of a quality equal to or better than those obtainable in present systems, At the same time, it will also permit images to be developed a plurality of times so that those images which contain large or extended solid areas can be more completely developed than is possible with conventional systems. The reason why the present inven tion is able to do this can perhaps be better understood by briefly describing the operation of conventional copiers.
  • the width of gap 4 is kept at a relatively large size, for example, 250 mils.
  • the carrier beads tend to fall through the gap quite freely at a velocity which is significantly higher than the velocity of the drum surface (which is preferably about lO inches/sec. for ap proximately 5 inch diameter drum) e.g. twice as fast or more.
  • This high developer velocity is provided intentionally and generally believed to be necessary so as to ensure that an adequate supply of fresh toner will be supplied to all areas of the latent image as it is passing through the development station.
  • the number of development cycles desired without image transfer to belt 8 can be selected as desired by means of control 21 mounted in the machine console. If the image contains primarily line copy, a single development is generally all that is needed. If, however, there are extended dark areas on the image, additional cycles, as required, can be provided merely by turning the dial on control 21. Although essentially as many development cycles as desired can be carried out, (the present invention has actually been practiced with more than 10 cycles without image degradation) the image is usually fully developed after about three cycles and this is all that shouldnormally be necessary. After the desired inumber .of development cycles has been carried out, control 21 willautomatically actuate roller 12 and belt driving rollers 9 11 to move the belt 8 into contact with the drum for transfer of the image thereto.
  • a development station for electrophotographic copiers which can selectively be controlled to develop an image as many times as desired or as needed for the particular type of image being copied.
  • Thesystem is highly efficient because all that is required-is that a single control be adjusted. If there are no extended dark areas on the image, a single development is all that is required and the system will work as fast and as efficiently as any other. If there are extended dark areas on the image, it will, of course, take longer to produce copies but this will be more than compensated for by the better quality image.
  • an electrophotographic copying apparatus including:
  • first support medium carrying a latent electrostatic image to be developed thereon
  • second support medium for receiving the developed image from said first support medium
  • transfer means for transferring said developed image from said first support medium to said second support medium
  • developing means for developing said latent electrostatic image on said first support medium prior to the transfer thereof to said second support medium by said transfer means, the improvement comprismg:
  • said developing means includes control means for selectively controlling the number of times that said latent electrostatic image is developed prior to the transfer thereof from said first support medium to said second support medium by said transfer means.
  • control means further includes selection means for selecting the number of times that said latent electrostatic image is to be developed prior to the transfer thereof from said first support medium to said second support medium, said number of times being from one to at least three.
  • control means includes means coupled to said drive means for passing said latent electrostatic image through said development station said selected number of times prior to the transfer thereof from said first support medium to said second support medium.
  • said devel oper supplying means includes means for passing said developer through said development station at a velocity substantially equal to the velocity that said latent electrostatic image is passed through said development station by said drive means.
  • said development station further includes a development plate spaced from said first support medium to define a narrow gap therebetween, at least a portion of said gap having a width of less than about 100 mils. and wherein said means for passing said developer through said development station comprises means for dropping said developer through said gap, the narrow width of said gap causing said developer to fall at a velocity substantially equal to the velocity of said latent electrostatic image.
  • said first support medium comprises a rotatable drum having a surface upon which said latent electrostatic image is formed.
  • said transfer means includes means coupled to said control means for bringing said second support medium into contact with said first support medium after said selected number of developing steps for transferring said developed image from said first medium to said second medium.
  • Electrophotographic copying apparatus comprismg:
  • control means for controlling the number of times that said latent electrostatic image is developed prior to the transfer thereof from said first support medium to said second support medium by said transfer means.
  • control means includes selection means for selecting the number of times that said latent electrostatic image is to be developed prior to the transfer thereof from said first support medium to said second support medium, said number of times being from one to at least two.
  • control means includes means coupled to said drive means for passing said latent electrostatic image through said development station a selected number of times prior to the transfer thereof from said first support medium to said second support medium.
  • said developer supplying means includes means for passing said developer through said development station at a velocity substantially equal to the velocity that said latent electrostatic image is passed through said development station by said drive means.
  • said development station further includes a development plate spaced from said support medium to define a narrow gap therebetween, at least a portion of said gap having a width of less than about mils. and wherein said means for passing said developer through said development station comprises means for dropping said developer through said gap by gravity, the narrow width of said gap causing said developer to fall at velocity substantially equal to the velocity of said latent electro-

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dry Development In Electrophotography (AREA)
  • Combination Of More Than One Step In Electrophotography (AREA)
US482040A 1974-06-24 1974-06-24 Multiple development method and apparatus for electrophotographic copiers Expired - Lifetime US3921571A (en)

Priority Applications (11)

Application Number Priority Date Filing Date Title
US482040A US3921571A (en) 1974-06-24 1974-06-24 Multiple development method and apparatus for electrophotographic copiers
CA225,258A CA1058980A (en) 1974-06-24 1975-04-23 Multiple development method and apparatus for electrophotographic copiers
GB16750/75A GB1495429A (en) 1974-06-24 1975-04-23 Multiple development method and apparatus for electrophotographic copiers
NL7507130A NL7507130A (nl) 1974-06-24 1975-06-16 Elektrofotografisch copieerapparaat.
FR7519177A FR2276617A1 (fr) 1974-06-24 1975-06-19 Machine a copier electro-photographique
IT24613/75A IT1039178B (it) 1974-06-24 1975-06-20 Apparecchiatura e procedimento di copiatura elettrofotografica
AU82348/75A AU496269B2 (en) 1974-06-24 1975-06-23 Multiple development method and apparatus for electrophotographic copiers
SE7507188A SE407118B (sv) 1974-06-24 1975-06-23 Elektrofotografisk kopieringsapparat
DE2528109A DE2528109C2 (de) 1974-06-24 1975-06-24 Elektrofotografisches Kopiergerät
JP50077095A JPS5118548A (enrdf_load_stackoverflow) 1974-06-24 1975-06-24
BE157634A BE830585A (fr) 1974-06-24 1975-06-24 Machine a copier electro-photographique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US482040A US3921571A (en) 1974-06-24 1974-06-24 Multiple development method and apparatus for electrophotographic copiers

Publications (1)

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US3921571A true US3921571A (en) 1975-11-25

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US482040A Expired - Lifetime US3921571A (en) 1974-06-24 1974-06-24 Multiple development method and apparatus for electrophotographic copiers

Country Status (10)

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US (1) US3921571A (enrdf_load_stackoverflow)
JP (1) JPS5118548A (enrdf_load_stackoverflow)
BE (1) BE830585A (enrdf_load_stackoverflow)
CA (1) CA1058980A (enrdf_load_stackoverflow)
DE (1) DE2528109C2 (enrdf_load_stackoverflow)
FR (1) FR2276617A1 (enrdf_load_stackoverflow)
GB (1) GB1495429A (enrdf_load_stackoverflow)
IT (1) IT1039178B (enrdf_load_stackoverflow)
NL (1) NL7507130A (enrdf_load_stackoverflow)
SE (1) SE407118B (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3991712A (en) * 1974-01-02 1976-11-16 Itek Corporation Cascade development station having a roughened development plate for enhancing developer mixture turbulence
US4007707A (en) * 1975-01-21 1977-02-15 Itek Corporation Xerographic development apparatus having a large reservoir for controlled flow through a narrow development zone
FR2362430A1 (fr) * 1976-08-19 1978-03-17 Oce Van Der Grinten Nv Dispositif de developpement a brosse magnetique
US20170031267A1 (en) * 2015-07-31 2017-02-02 Canon Kabushiki Kaisha Developing device, process cartridge, and image forming apparatus

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS53126399A (en) * 1977-04-05 1978-11-04 Santo Tekkosho Kk Continuous mercerizing finish of tubular knitted fabric
JPS5851559B2 (ja) * 1977-07-07 1983-11-17 株式会社山東鉄工所 布帛の連続染色洗浄方法及び装置
BE800531A (fr) * 1978-11-27 1973-10-01 Tongaat Sugar Pty Ltd Broyeur a marteaux pour defibreur utilisable notamment dans l'industrie sucriere
JPH0121994Y2 (enrdf_load_stackoverflow) * 1985-07-11 1989-06-29

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3592642A (en) * 1966-11-21 1971-07-13 Xerox Corp Duplicating method wherein a paper sheet heated to the melting point of a toner image simultaneously causes the transfer of the toner from the photoconductor and fusing of the toner image on the paper sheet
US3736055A (en) * 1971-12-17 1973-05-29 Ibm Reproduction apparatus incorporating alternate redevelopment and reimaging cycles for multiple copies
US3754531A (en) * 1971-07-14 1973-08-28 Xerox Corp Fluidized development apparatus
US3754963A (en) * 1970-12-23 1973-08-28 Ibm Surface for impression development in electrophotography

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1047757A (en) * 1974-01-02 1979-02-06 William R. Buchan Cascade development station having a roughened development plate for enhancing developer mixture turbulence

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3592642A (en) * 1966-11-21 1971-07-13 Xerox Corp Duplicating method wherein a paper sheet heated to the melting point of a toner image simultaneously causes the transfer of the toner from the photoconductor and fusing of the toner image on the paper sheet
US3754963A (en) * 1970-12-23 1973-08-28 Ibm Surface for impression development in electrophotography
US3754531A (en) * 1971-07-14 1973-08-28 Xerox Corp Fluidized development apparatus
US3736055A (en) * 1971-12-17 1973-05-29 Ibm Reproduction apparatus incorporating alternate redevelopment and reimaging cycles for multiple copies

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3991712A (en) * 1974-01-02 1976-11-16 Itek Corporation Cascade development station having a roughened development plate for enhancing developer mixture turbulence
US4007707A (en) * 1975-01-21 1977-02-15 Itek Corporation Xerographic development apparatus having a large reservoir for controlled flow through a narrow development zone
FR2362430A1 (fr) * 1976-08-19 1978-03-17 Oce Van Der Grinten Nv Dispositif de developpement a brosse magnetique
US4132192A (en) * 1976-08-19 1979-01-02 Oce-Van Der Grinten N.V. Magnetic brush developing apparatus
US20170031267A1 (en) * 2015-07-31 2017-02-02 Canon Kabushiki Kaisha Developing device, process cartridge, and image forming apparatus
US9835975B2 (en) * 2015-07-31 2017-12-05 Canon Kabushiki Kaisha Developing device, process cartridge, and image forming apparatus

Also Published As

Publication number Publication date
JPS5118548A (enrdf_load_stackoverflow) 1976-02-14
GB1495429A (en) 1977-12-21
CA1058980A (en) 1979-07-24
DE2528109A1 (de) 1976-01-15
FR2276617B1 (enrdf_load_stackoverflow) 1982-03-26
IT1039178B (it) 1979-12-10
FR2276617A1 (fr) 1976-01-23
BE830585A (fr) 1975-12-24
SE7507188L (sv) 1975-12-29
DE2528109C2 (de) 1983-12-29
SE407118B (sv) 1979-03-12
NL7507130A (nl) 1975-12-30
AU8234875A (en) 1977-01-06

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