US3550555A - Xerographic developer separation - Google Patents

Xerographic developer separation Download PDF

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Publication number
US3550555A
US3550555A US659520A US3550555DA US3550555A US 3550555 A US3550555 A US 3550555A US 659520 A US659520 A US 659520A US 3550555D A US3550555D A US 3550555DA US 3550555 A US3550555 A US 3550555A
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US
United States
Prior art keywords
developer
toner
xerographic
development
chute
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
US659520A
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English (en)
Inventor
Frederick W Hudson
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Xerox Corp
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Xerox Corp
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Publication date
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Publication of US3550555A publication Critical patent/US3550555A/en
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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
    • 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
    • G03G15/0822—Arrangements for preparing, mixing, supplying or dispensing developer
    • G03G15/0887—Arrangements for conveying and conditioning developer in the developing unit, e.g. agitating, removing impurities or humidity
    • 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
    • G03G15/0822—Arrangements for preparing, mixing, supplying or dispensing developer
    • G03G15/0887—Arrangements for conveying and conditioning developer in the developing unit, e.g. agitating, removing impurities or humidity
    • G03G15/0891—Arrangements for conveying and conditioning developer in the developing unit, e.g. agitating, removing impurities or humidity for conveying or circulating developer, e.g. augers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S222/00—Dispensing
    • Y10S222/01—Xerography

Definitions

  • a vibrating tray offset from the horizontal, is positioned to receive over-toned two-component xerographic developer mix comprising carrier granules and excess toner particles.
  • carrier granules As the developer is deposited on the tray, optimumly toned carrier granules will move towards the lower end of the tray for use in the development of latent electrostatic images. Excess toner particles will move in the opposite direction for being removed from the mixture.
  • a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. ln the usual method of carrying out the process, the xerographic plate is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.
  • the latent electrostatic image can then be developed by contacting it with a finely divided electrostatically attractable material such as a resinous powder.
  • a finely divided electrostatically attractable material such as a resinous powder.
  • the powder is held in image areas by the electrostatic charges on the layer. Where the charge is greatest, the greatest amount of material is deposited; and where the charge is least, little or no material is deposited.
  • a powder image is produced in conformity with the light image of the copy being reproduced.
  • the powder is subsequently transferred to a sheet of paper or other surface and suitably affixed to thereby form a permanent print.
  • the electrostatically attractable developing material com monly used in xerography consists of a pigmented resinous powder referred to here as toner and a carrier" of larger granular beads formed with glass, sand or steel cores coated with a material removed in the triboelectric series from the toner so that a triboelectric charge is generated between the toner powder and the granular carrier. Such charge causes the toner to adhere to the carrier.
  • the carrier also provides mechanical control so that the toner can be readily handled and brought into contact with the exposed xerographic surface. The toner is then attracted to the electrostatic image to produce a visible powder image on the xerographic surface.
  • Toner particles which are mixed with carrier adhere to and coat the surface of the carrier due to the electrostatic attraction between them.
  • This two-component mixture of carrier and toner constitutes the developer mixture.
  • Toner-coated carrier moves across the xerographic surface at which time toner particles are electrostatically pulled away from the carrier by the charged areas of the surface and are selectively deposited thereon to form a visible powder image.
  • the partially denuded carrier then moves beyond the xerographic surface.
  • additional toner powder is generally supplied to the developer mixture in proportion to the amount of toner deposited on the xerographic surface.
  • the percentof toner particles to carrier granules within a developer mixture is generally referred to as the toner concentration.
  • the toner concentration When there are insufiicient toner particles with a given quantity of carrier granules in the developer mixture, these toner particles will be tightly bonded to the carrier granules by the electrostatic forces therebetween.
  • the charges in the image areas are insufficiently strong to electrostatically attract sufficienttoner particles away from the carrier granules.
  • insufficient toner particles will be available for the development of images. lmages developed with developer mixtures of a low toner concentration produce undesirably light copy.
  • the electrostatic force bonding toner particles to carrier granules is inversely proportional to the amount of toner particles on a carrier granule.
  • the instant invention achieves the proper ratio of toner to carrier for any two-component developer mixture to ensure optimum development.
  • Optimum toner concentration is dependent on the atmospheric conditions in which the xerographic development is carried out. This is because the electrostatic bond between toner and carrier is inversely proportional to humidity. For example, if a xerographic machine were operated with a two-component developer mixture having a toner concentration optimum for an average humidity, it will develop optimumly at an average humidity. lf however, the same machine with the same developer were operated at a high humidity, the copy produced would be overly dark since toner would be given up to the image area charges too easily due to the decreased toner-to-carrier bond caused by the high humidity. This humidity problem also exists for low humidity.
  • developer When, however, developer is separated in accordance with the instant invention, the same humidity factors affecting development are also present at the developer separating station. Consequently, developer may be supplied from the separator at a toner concentration optimum for the atmospheric conditions at which the xerographic development takes place.
  • toner when toner is added to the developer it is generally added equally across the length of the development zone. If, however, the image being reproduced has large dark sections in one area, as the middle, then the central portions of the developer mixture would be reduced to a lesser toner concentration than the side portions. The addition of toner to the developer evenly across the length of the development zone would not rectify this inbalance.
  • the present invention contemplates overcoming the problems of maintaining optimum toner concentration of twodeveloper by sorting out the excess toner particles from the developer mixture prior to xerographic development. In one mode of operation, this can be carried out immediately before the xerographic development step within a xerographic reproducing machine.
  • lt is another object of the present invention to remove excess toner particles from two-component xerographic developer.
  • Another object of the present invention is to prepare quantities of two-component developer having toner concentrations which are optimum for the atmospheric conditions at which it is prepared.
  • Another object of the invention is to control toner concentration across the length of xerographic development zones.
  • Another object of the invention is to mechanically separate two-component xerographic developer into optimumly toned carrier granules and excess toner particles.
  • FIG. 1 is a diagrammatic sectional view illustrating developer separating apparatus operable in accordance with the principles of the instant invention as incorporated in a xerographic machine adapted for continuous and automatic use.
  • FIG. 2 is a perspective view showing the developer separating unit removed from the xerographic machine.
  • FIG. 1 Shown in the FIG. 1 is a xerographic machine employing a developer separator constructed in accordance with the instant invention.
  • the elements of this machine which is constructed for continuous and automatic operation, are all conventional in the xerographic arts except for the novel developer separator.
  • the several xerographic processing stations in the path of movement of the xerographic surface for each machine may be briefly described as follows:
  • a charging station A at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;
  • An exposure station B at which the light or radiation pattern of copy to be reproduced is projected onto the drum surface to dissipate the drum charge in the exposed areas thereof to thereby leave a latent electrostatic image of the copy to be reproduced;
  • a developing station C at which a xerographic developing material, including toner particles having an electrostatic charge opposite to that of the electrostatic latent image, are cascaded across the drum surface, whereby the toner particles adhere to the electrostatic latent image to form a xerographic powdered image in the configuration of the copy being reproduced;
  • a transfer station D at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer material or a support surface;
  • a drum cleaning and discharge station E at which the drum surface is brushed to remove residual toner particles remaining thereon after image transfer, and at which the drum surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.
  • the latent electrostatic images to be developed are formed on a xerographic surface formed in the shape of a drum or other cylinder.
  • the drum is adapted to be rotated about its axis by a main drum drive shaft 12 by any conventional power source. not shown. The movement of the drum permits its surface to be moved past the various processing stations including the development zone.
  • the developing instrumentalities are preferably confined within a housing 14 having a lower sump portion 16 adapted to contain a supply of over-toned two-component developer material.
  • a conveyor assembly 18 is provided within the housing 14 to raise developer from within the sump to a raised location for cascading across the xerographic surface in the development zone 20.
  • the conveyor assembly comprises a belt 22 formed with elongated buckets 24 thereon.
  • the belt is trained for movement by rollers 26, at least one of which is power driven to move the belt 22 and buckets 24 in the direction of the arrow as shown.
  • a pickoff baffle 30 guides the developer as it falls away from the xerographic surface and directs the developer back into the sump 16.
  • the developer sorting instrumentalities which can be seen more clearly in FIG. 2, are positioned within the development housing 14 to intercept the developer as it moves from the buckets 24 to the guide plate 28 adjacent the xerographic development zone 20.
  • the developer sorting instrumentalities are generally designated by numeral 32 and are positioned within the housing on a support member 34 secured at its ends to the end faces of the developer housing.
  • the chute 38 is inclined with respect to the horizontal at an angle of about 15. Angles from about 10 to 20 may be also employed. It has a lower end 42 positionable over the guide plates 28 to direct the flow of developer into the development zone 20.
  • the chute 38 also has an upper end 40 of sufficient length as to permit excess toner particles moved thereacross to fall back into the sump 16.
  • the chute also has sidewalls 44 to prohibit the movement of developer toner from moving beyond the sides of the chute.
  • sump 46, buckets 24, funnel-shaped member 36 and chute 38 should be equal to the length of the xerographic surface 10. In this manner, developer will be cascaded across the length of image bearing surface for developing the entire image.
  • the funnel-shaped member 36 is rigidly held in position with respect to base 34 by a pair of end plates 36.
  • the chute member 38 is held in position between the funnel-shaped member 36 and base 34 by a pair of leaf spring elements 48 which permit the reciprocation of the chute with respect to the base plate 34 and the funnel-shaped member 36.
  • the lower ends of these springs are rigidly secured to the base plate 34 and chute 38.
  • Motion is imparted to the chute by an electromagnetic motor.
  • the motor includes a first terminal 50 rigidly secured with respect to the upper end of the leaf springs 48 and chute 38.
  • a coacting second terminal 52 is rigidly secured to an alternating source of potential 54.
  • the alternating source of potential When the alternating source of potential is activated, it will intermittently cause terminal 50 to be drawn towards terminal 52 to move terminal 52 and chute 38 towards the source of power.
  • the source of alternating power is reversed, the attraction between the terminals is terminated and the leaf spring causes the chute to return to a normal position with the terminals 50 and 52 separated.
  • the source of alternating potential is operating in a normal fashion, the action between the two terminals causes an extremely rapid pulsation between the terminals and vibrates the chute at a very high rate.
  • a source of alternating potential of the type described can vibrate the chute 38 at a frequency of about 60 cycles a second and at an amplitude from between one thirty-second of an inch to one sixty-fourth of an inch. Such frequency and amplitude has been found sufficient to cause the separation of developer at a rate adequate for incorporation in a xerographic machine.
  • the atmospheric conditions at which two-component xerographic development takes place affects the quality of development.
  • the same toner concentration can thus produce overly light, overly dark or optimum copy depending on the humidity at which the development occurs.
  • developer is prepared in accordance with the instant invention for use in a machine at the same atmospheric conditions, optimum toner concentration and optimum development are ensured. This is because the carrier granules in the development zone 20 have the same electrostatic attractive force for toner as they-do on the developer separating chute 28. Consequently, optimumly toned carrier will be prepared and delivered tothe development zone regardless of the humidity at which the apparatus is operated.
  • the toner separator unit of the instant invention is readily incorporated into a xerographic machine employing cascade development.
  • the developer mixture of an optimum toner concentration need not necessarily be used, however, for cascade development. It could readily be introduced into a xerographic reproducing machine employing development instrumentalities of the magnetic brush, fluidized bed or any of the known two-component development systems.
  • the toner separator unit could be employed to provide optimumly toned developer for storage and subsequent sue in xerographic development. As such, its" utility is not necessarily linked to its use in combination with a xerographic reproducing machine.
  • developer moved thereacross has an ability to cause complete interaction between the toner and carrier to effect a complete rubbing between the two components. This permits the complete triboelectric charging of all toner particles moved into the development zone. Consequently, by employing the toner separator of the instant invention all the developer supplied to the development zone includes fully charged toner particles, fully toned carrier granules and no uncharged or unassociated toner particles to be intermixed therewith. This type of developer mix is generally considered fully blended.
  • a xerographic reproducing machine of the type having a sump for containing a quantity of two-component developer comprising carrier granules and charged toner particles, elevating means to raise the developer to an elevated location for cascading the developer across the latent electrostatic image bearing surface for the development thereof and means to direct the cascaded developer back to the sump, the improvement comprising:
  • a developer guiding chute positioned in the path of flow of the developer to direct the developer from the elevating means towards a surface to be developed
  • the motor means includes a chute pulsing motor capable of reciprocating the chute within its plane of orientation.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Brush Developing In Electrophotography (AREA)
  • Dry Development In Electrophotography (AREA)
US659520A 1967-08-09 1967-08-09 Xerographic developer separation Expired - Lifetime US3550555A (en)

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US65952067A 1967-08-09 1967-08-09

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3754531A (en) * 1971-07-14 1973-08-28 Xerox Corp Fluidized development apparatus
US3999512A (en) * 1974-09-25 1976-12-28 Xerox Corporation Electrostatic development system with passive storage capacity
US4794878A (en) * 1987-08-03 1989-01-03 Xerox Corporation Ultrasonics traveling wave for toner transport
US5012289A (en) * 1989-08-11 1991-04-30 International Business Machines Corporation Toner metering apparatus
US5229823A (en) * 1992-01-30 1993-07-20 Eastman Kodak Company Toner agitator system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4583645A (en) * 1982-12-02 1986-04-22 Shoichi Yamamoto Vibratory grain separating apparatus used with rice-hulling apparatus

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3754531A (en) * 1971-07-14 1973-08-28 Xerox Corp Fluidized development apparatus
US3999512A (en) * 1974-09-25 1976-12-28 Xerox Corporation Electrostatic development system with passive storage capacity
US4794878A (en) * 1987-08-03 1989-01-03 Xerox Corporation Ultrasonics traveling wave for toner transport
US5012289A (en) * 1989-08-11 1991-04-30 International Business Machines Corporation Toner metering apparatus
US5229823A (en) * 1992-01-30 1993-07-20 Eastman Kodak Company Toner agitator system

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