EP0018078B1 - Gerät zur Entwicklung eines elektrostatischen Ladungsbildes - Google Patents

Gerät zur Entwicklung eines elektrostatischen Ladungsbildes Download PDF

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Publication number
EP0018078B1
EP0018078B1 EP19800300765 EP80300765A EP0018078B1 EP 0018078 B1 EP0018078 B1 EP 0018078B1 EP 19800300765 EP19800300765 EP 19800300765 EP 80300765 A EP80300765 A EP 80300765A EP 0018078 B1 EP0018078 B1 EP 0018078B1
Authority
EP
European Patent Office
Prior art keywords
fibres
tubular member
magnetic
particles
tufts
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
Application number
EP19800300765
Other languages
English (en)
French (fr)
Other versions
EP0018078A1 (de
Inventor
Paul William Burnham
Eugene F. Young
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.)
Xerox Corp
Original Assignee
Xerox 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 US06/047,615 external-priority patent/US4240740A/en
Application filed by Xerox Corp filed Critical Xerox Corp
Publication of EP0018078A1 publication Critical patent/EP0018078A1/de
Application granted granted Critical
Publication of EP0018078B1 publication Critical patent/EP0018078B1/de
Expired legal-status Critical Current

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Classifications

    • 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
    • G03G15/09—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer using magnetic brush
    • G03G15/0921—Details concerning the magnetic brush roller structure, e.g. magnet configuration
    • G03G15/0928—Details concerning the magnetic brush roller structure, e.g. magnet configuration relating to the shell, e.g. structure, composition

Definitions

  • This invention relates generally to an apparatus for developing a latent electrostatic image with magnetic particles.
  • An apparatus of this type is frequently employed in an electrophotographic printing machine.
  • an electrophotographic printing machine includes a photoconductive member which is charged to a substantially uniform potential to sensitize its surface. The charged portion of the photoconductive surface is exposed to an optical image of an original document being reproduced. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer mix into contact therewith. This forms a powder image on the photoconductive member which is subsequently transferred to a copy sheet. Finally, the copy sheet is heated to affix the powder image thereto.
  • the developer mix comprises toner particles adhering triboelectrically to carrier granules.
  • This two-component mixture is brought into contact with the latent image.
  • the toner particles are attracted from the carrier granules to the latent image to form the powder image thereof.
  • the developer material particles have low resistivities, e.g. the resistivity ranges from about 10 4 to about 10 9 ohm-centimeters.
  • the resistivity ranges from about 10 4 to about 10 9 ohm-centimeters.
  • transfer is optimized by employing particles having high resistivities.
  • the printing machine is faced with two contradictory requirements, i.e. the utilization of particles having low resistivity for optimum development, and having high resistivity for optimum transfer. It has been found that when more-resistive particles are employed, they frequently produce images having portions of the solid areas unreproduced.
  • Various approaches have been devised to improve development.
  • Cross discloses a rotatable non-magnetic cylinder having iron helices thereon.
  • the cylinder rotates in a container having magnets mounted externally thereof.
  • Solarck describes a woven pile brush having a mixture of non-conductive and conductive pile fibres.
  • the conductive pile fibres are shorter than the non-conductive fibres, and can function as a development electrode while avoiding contact with the latent image.
  • Miller discloses a pair of metallised fur brushes having individual flexible filaments coated with a thin layer of an electrically conductive metal.
  • One brush is of low electrical conductivity, while the other is of high electrical conductivity.
  • the Japanese patent application discloses a permanent magnet disposed inside a rotatable cylindrical non-magnetic sleeve.
  • a fibre brush whose volume electrical resistance ranges from about 10 6 to about 10 11 ohm-centimeters and whose height ranges from about 0.5 to about 10 mm, is secured to the outer periphery of the non-magnetic sleeve.
  • an apparatus for developing an electrostatic latent image with magnetic toner particles including a tubular member having a multiplicity of magnetic fibres extending outwardly therefrom and an internal elongated magnetic member. At least a portion of the fibres have their free ends contacting the surface carrying the latent image. Relative movement between the tubular and magnetic members causes the free ends of the fibres to move both circumferentially and laterally under the influence of the moving magnetic field so that the particles move along the fibres into contact with the latent image. As the particles are being deposited on the latent image, the fibre movement also deposits the particles substantially-uniformly over the image.
  • FIG. 1 schematically depicts the various components of an illustrative electrophotographic printing machine incorporating the development apparatus of the present invention therein. It will become evident from the following discussion that the development apparatus is equally well suited for use in a wide variety of electrostatographic printing machines, and is not necessarily limited in its application to the particular embodiments shown herein.
  • the illustrative electrophotographic printing machine employs a drum 10 having a photoconductive surface 12.
  • photoconductive surface 12 comprises a transport layer containing small molecules dispersed in an organic resinous material, and a generation layer having selenium dispersed in a resinous material.
  • Drum 10 moves in the direction of arrow 14 to advance successive portions of photoconductive surface 12 sequentially through the various processing stations disposed about the path of movement thereof.
  • a portion of photoconductive surface 12 passes through charging station A where a corona generating device, indicated generally by the reference numeral 16, charges photoconductive surface 12 to a relatively high substantially uniform potential.
  • the charged portion of photoconductive surface 12 is advanced through exposure station B including exposure system 18, wherein an original document is positioned face-down upon a transparent platen.
  • the light rays reflected from the original document are transmitted through a lens to form an optical image thereof.
  • the image is projected onto the charged portion of photoconductive surface 12 to dissipate the charge thereon selectively.
  • This records an electrostatic latent image on photoconductive surface 12 corresponding with the indicia on the original document.
  • drum 10 advances the electrostatic latent image on photoconductive surface 12 to development station C.
  • a magnetic fibre brush development system At development station C, a magnetic fibre brush development system, indicated generally by the reference numerals 20, advances magnetic particles into contact with the electrostatic latent image.
  • the latent image attracts the particles, forming a particle image on photoconductive surface 12 of drum 10.
  • the detailed structure of the development system will be described hereinafter with reference to Figures 2 through 7, inclusive.
  • Drum 10 then advances the particle image to transfer station D at which a sheet of support material is moved into contact with the particle image.
  • the sheet of support material is advanced to transfer station D by sheet feeding apparatus indicated generally by the reference numeral 22.
  • sheet feeding apparatus 22 includes a feed roll 24 contacting the uppermost sheet of a stack of sheets 26.
  • Feed roll 24 rotates in the direction of arrow 28 so as to advance the uppermost sheet into the nip defined by forwarding rollers 30.
  • Forwarding rollers 30 rotate in the direction of arrow 32 to advance the sheet into chute 34.
  • Chute 34 directs the advancing sheet of support material into contact with the photoconductive surface of drum 10 so that the particle image developed thereon contacts the advancing sheet at transfer station D.
  • Transfer station D includes a corona generating device 36 which sprays ions onto the back of the sheet. This attracts the particle image from photoconductive surface 12 to the sheet. After transfer, the sheet continues to move in the direction of arrow 38 onto a conveyor 40 which advances the sheet to fusing station E.
  • Fusing station E includes a fuser assembly, indicated generally by the reference numeral 42, which permanently affixes the transferred particle image to the sheet.
  • fuser assembly 42 includes a heated fuser roller 44 and a back-up roller 46. The sheet passes between fuser roller 44 and back-up roller 46 with the particle image contacting fuser roller 44. In this manner, the particle image is permanently affixed to the sheet.
  • the forwarding rollers 48 advance the sheet to catch tray 50 for subsequent removal from the printing machine by the operator.
  • Cleaning station F includes a rotatably mounted fibrous brush in contact with photoconductive surface 12. The particles are cleaned from photoconductive surface 12 by the rotation of the brush in contact therewith. Subsequent to cleaning, a discharge lamp (not shown) floods photoconductive surface 12 with light to dissipate any residual electrostatic charge remaining thereon prior to the charging thereof for the next successive image cycle.
  • development system 20 includes a hopper 52 storing a supply of magnetic particles 54 therein. Particles 54 descend through aperture 56 in hopper 52 onto the surface of developer roller 58.
  • Developer roller 58 includes an elongated cylindrical magnet 60 mounted interiorly of a relatively-movable tubular member 62.
  • a tubular sleeve 64 fits over tubular member 62.
  • tubular sleeve 64 is made from a fabric and has a multiplicity of stainless steel tufts 66 extending outwardly therefrom.
  • Sleeve 64 is preferably cemented to tubular member 62.
  • a voltage source (not shown) electrically biases sleeve 64 to a suitable magnitude and polarity to effect development of the latent image with the magnetic particles.
  • Each tuft 66 on sleeve 64 includes a multiplicity of stainless steel fibres. Tufts 66 contact photoconductive surface 12 of drum 10 in development zone 68. Thus, as the particles 54 are being deposited on the latent image recorded on photoconductive surface 12, tufts 66 are in contact therewith. Tufts 66 extend about the entire circumferential surface of tubular member 62.
  • Tubular member 62 is made from a non-magnetic material, such as aluminium.
  • magnet 60 is made from barium ferrite having a permanent magnetic field.
  • Tubular member 62 rotates in the direction of arrow 70.
  • the angular velocity of tubular member 70 is such that the tangential velocity thereof is equal to the tangential velocity of drum 10.
  • Magnetic member 60 rotates, in the direction of arrow 72, at an angular velocity greater than the angular velocity of tubular member 62.
  • magnetic member 60 may rotate in a direction opposed to arrow 72.
  • magnet 60 moves relatively to sleeve 64 particles 54 are transported over and around tufts 66. This is because magnetic dipoles are set up in each fibre of tufts 66, which causes movement of the free end of each fibre. It is necessary to move the free end of each fibre of tufts 66 both circumferentially and laterally.
  • each tuft fibre may be achieved by employing fibres having differing magnetic properties, in which case magnetic fields of varying strength are established between the fibre ends. Fibre motion is dependent upon the magnetic field gradient at any point on the fibre. This results in the fibres moving in all directions.
  • both circumferential and lateral movement of each tuft fibre may be achieved by forming magnet 60 with a helical magnetic pattern as shown more clearly in Figure 3.
  • FIG. 3 shows developer roller 58 in greater detail.
  • Magnet 60 is mounted rotatably within tube 62 and has a helical magnetic pole pattern 74 formed thereon.
  • the helix angle is about 74°, e.g., one turn per 25 mm axial length for a 28 mm diameter magnet.
  • Tube 62 and magnet 60 are rotated by a constant speed drive motor 68.
  • the gears coupling motor 61 with magnet 60 and tube 62 are selected such that magnet 60 rotates at a greater angular velocity than tube 62.
  • tube 62 is rotated at an angular velocity such that the tangential velocity thereof is substantially equal to the tangential velocity of drum 10.
  • the magnetic particles When magnet 60 has a helical pole pattern 74 formed thereon, the magnetic particles will advance in a lateral direction i.e. substantially parallel to the longitudinal axis of tubular member 62 as well as circumferentially. Thus, the unused magnetic particles will progress toward one end of tubular member 62. In order to prevent these particles from cascading over photoconductive surface 12, they must be collected and returned to hopper 52 for subsequent re-use.
  • a housing (not shown) is located at one end of tubular member 62 for receiving the unused particles.
  • a particle transport (not shown), e.g. a helical auger or bead chain, returns the particles to hopper 52.
  • hopper 52 houses a supply of magnetic particles 54 which descend through aperture 56 onto tubular member 74.
  • An elongated cylindrical magnet 76 is disposed interiorly of tubular member 74.
  • Tubular member 74 remains substantially stationary while magnetic member 76 rotates in the direction of arrow 78.
  • An arcuate fabric member 80 is secured to tubular member 74.
  • fabric member 80 is cemented to tubular member 74 in development zone 82. The position of fabric member 80 is optimized with reference to development zone 82.
  • a multiplicity of tufts 84 extend in an outward direction from fabric 80. Each tuft is woven through fabric 80 and comprises a multiplicity of fibres.
  • Each tuft 84 is in contact with photoconductive surface 12 of drum 10 in development zone 82.
  • a voltage source electrically biases fabric 80 to a suitable magnitude and polarity to facilitate development.
  • Magnet 76 rotates in the direction of arrow 78 while tubular member 74 remains stationary.
  • particles 54 advance around tubular member 74 into development zone 82.
  • particles 54 move around and over tufts 84 and are deposited on the latent image recorded on photoconductive surface 12 of drum 10.
  • the free end of each fibre moves as magnet 76 rotates in the direction of arrow 78.
  • magnetic dipoles are set up in each fibre producing movement thereof.
  • tubular member 74 is made from a non-magnetic material such as aluminum.
  • Magnet 76 is preferably made from barium ferrite.
  • tubular member 74 having fabric 80 secured thereto in development zone 82.
  • fabric 80 extends over a small arcuate region, the length thereof being defined by development zone 82.
  • Tufts 84 are of sufficient length to have the free end portions thereof contacting photoconductive surface 12.
  • drive motor 75 rotates magnet 76, particles 54, move around tubular member 74 and into development zone 82. In development zone 82, particles 54 contact the moving tuft fibres.
  • Motor 75 is preferably a constant speed motor. This ensures that the particle image deposited on photoconductive surface 12 of drum 10 is substantially uniform.
  • Each tuft 66 includes a multiplicity of stainless steel fibres 86.
  • Each group of fibres 86 forming tufts 66 passes through fabric 64 in a W-shaped configuration.
  • the tufts 66 are spaced uniformly apart by distance d.
  • FIG. 7 An alternative method of weaving a tuft 66 in fabric 64 is shown in Figure 7. As depicted thereat, each fibre 86 of each tuft 66 passes through fabric 64 in a U-shaped configuration. Once again, the inter-tuft distance d is maintained.
  • the fabric is preferably made from cotton having an electro-conductive coating of black latex heavily loaded with carbon thereon.
  • each tuft has from about 500 to about 1500 fibres therein.
  • Each fibre ranges from about 0.005 to about 0.015 mm in diameter. It has been found that the density of tufts is important, and that too great a density prevents independent movement of each fibre and results in particle blockages, causing image streaking.
  • the distance d between adjacent tufts preferably ranges from 2.0 to 2.5 mm. It is desirable that the tufts be of sufficient length to form a fairly soft brush.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Woven Fabrics (AREA)
  • Dry Development In Electrophotography (AREA)
  • Cleaning In Electrography (AREA)

Claims (8)

1. Vorrichtung (20) zum Entwickeln eines von einer bewegbaren Fläche (12) getragenen elektrostatischen latenten Abbildes mittels magnetischen Partikeln (54), mit
einem langgestreckten röhrenförmigen Teil (74), der eine Vielzahl von magnetischen Fasern (84) aufweist, die von ihm nach außen hervorragen, wobei die maximale Radialerstreckung der Fasern größer ist als der Abstand zwischen dem Teil und der Fläche und wenigstens einige der Fasern die Fläche berühren.
einem langgestreckten magnetischen Teil (60), der innerhalb des röhrenförmigen Teils angeordnet ist und dessen Magnetfeld die Partikeln an den röhrenförmigen Teil anzieht, und
Mitteln (68) zum Erzeugen einer relativen Winkelbewegung zwischen dem röhrenförmigen und magnetischen Teil, wobei die Konstruktion des magnetischen Teils und der Fasern derart ist, daß die relative Drehung des Magnetfeldes an den Fasern vorbei deren freie Enden veranlaßt, sich relativ zu deren inneren Enden in Umfangsrichtung und in einer Richtung parallel zur Drehachse zu bewegen, um die Partikel zu veranlassen, sich unter Einwirkung des angelegten Magnetfeldes entlang den Fasern zu bewegen.
2. Vorrichtung nach Anspruch 1, in welcher die Fasern in Büscheln (66) zusammengruppiert sind, die an ihren Wurzeln mit gegenseitigen Abständen angeordnet sind.
3. Vorrichtung nach Anspruch 2, in welcher die Büschel mit im wesentlichen gleichen gegenseitigen Abständen (d) angeordnet sind.
4. Vorrichtung nach irgendeinem der vorhergehenden Ansprüche mit einem Gewebe (64), das an dem röhrenförmigen Teil befestigt ist und Fasern aufweist, die durch es hindurchgewebt sind.
5. Vorrichtung nach Anspruch 4, in welcher das Gewebe eine elektrisch leitfähige Beschichtung aufweist.
6. Vorrichtung nach irgendeinem der vorhergehenden Ansprüche, in welcher der röhrenförmige Teil stationär ist, und in welcher die Fasern von einem Bereich des röhrenförmigen Teils abstehen, welcher unmittelbar gegenüber der genannten Fläche angeordnet ist.
7. Vorrichtung nach irgendeinem der Ansprüche 1 bis 5, in welcher der röhrenförmige Teil bestimmt ist, gedreht zu werden, und in welcher die Fasern von der Gesamtheit der gekrümmten Fläche der röhrenförmigen Teils abstehen.
8. Vorrichtung nach irgendeinem der vorhergehenden Ansprüche, in welcher die Fasern aus einem magnetischen rostfreien Stahl bestehen.
EP19800300765 1979-03-26 1980-03-12 Gerät zur Entwicklung eines elektrostatischen Ladungsbildes Expired EP0018078B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US2393579A 1979-03-26 1979-03-26
US23935 1979-03-26
US47615 1979-06-11
US06/047,615 US4240740A (en) 1979-06-11 1979-06-11 Development system

Publications (2)

Publication Number Publication Date
EP0018078A1 EP0018078A1 (de) 1980-10-29
EP0018078B1 true EP0018078B1 (de) 1984-05-16

Family

ID=26697817

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19800300765 Expired EP0018078B1 (de) 1979-03-26 1980-03-12 Gerät zur Entwicklung eines elektrostatischen Ladungsbildes

Country Status (5)

Country Link
EP (1) EP0018078B1 (de)
AU (1) AU533116B2 (de)
BR (1) BR8001701A (de)
DE (1) DE3067806D1 (de)
MX (1) MX150104A (de)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4239017A (en) * 1979-07-16 1980-12-16 Xerox Corporation Development system

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB871041A (en) * 1956-10-11 1961-06-21 Mason & Sons Ltd E N Method of and apparatus for developing prints
US3246629A (en) * 1963-06-18 1966-04-19 Addressograph Multigraph Apparatus for developing electrostatic images
JPS4837382B1 (de) * 1968-08-26 1973-11-10
US3614221A (en) * 1969-12-30 1971-10-19 Xerox Corp Imaging system
US3664857A (en) * 1970-02-06 1972-05-23 Eastman Kodak Co Xerographic development apparatus and process
JPS5367438A (en) * 1976-11-29 1978-06-15 Hitachi Metals Ltd Magnet roll for use in magnetic toner

Also Published As

Publication number Publication date
MX150104A (es) 1984-03-15
AU5665480A (en) 1980-10-02
DE3067806D1 (en) 1984-06-20
AU533116B2 (en) 1983-11-03
BR8001701A (pt) 1980-11-18
EP0018078A1 (de) 1980-10-29

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