US3613637A - Developer for electrostatic images - Google Patents

Developer for electrostatic images Download PDF

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Publication number
US3613637A
US3613637A US833459A US3613637DA US3613637A US 3613637 A US3613637 A US 3613637A US 833459 A US833459 A US 833459A US 3613637D A US3613637D A US 3613637DA US 3613637 A US3613637 A US 3613637A
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United States
Prior art keywords
developer
bed
charge pattern
development
xerographic
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Expired - Lifetime
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US833459A
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English (en)
Inventor
Dinesh S Shah
John F Gardner
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Xerox Corp
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Xerox Corp
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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
    • G03G15/082—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer for immersion

Definitions

  • a xerographic surface comprising a layer of 5 photoconductive insulating material affixed to a conductive backing is used to support electrostatic images.
  • 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 charge pattern can then be developed by contacting it with the finely divided electrostatically attractable material such as resinous powder.
  • the powder is held in charge 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. Powder is subsequently transferred to a sheet of paper or other surface and suitably affixed thereto to form a permanent print.
  • the electrostatically attractable developing material commonly used in xerography consists of a pigmented resinous powder referred to here as toner and a granular material called carrier".
  • the carrier is usually coated with a material removed in the triboelectric series from the toner so that a triboelectric charge is generated between the powder and the granular carrier. Such charge causes the powder 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 surfaces. The powder particles are then attracted to the electrostatic images to produce a visible powder image on the xerographic surface.
  • cascade development the contact between the image and developing material, or developer, is achieved by pouring or cascading the two-component developer across the xerographic surface.
  • the individual carrier particles bounce or roll across the image-bearing surface contacting the image at randomly spaced points.
  • the amount of developer flowing across the xerographic surface and the number of contact points between the developer and the image areas control the degree of development or the quantities of toner deposited on image areas.
  • the developer flow, and the number of developer particles contacting each incremental area of the xerographic surface can be increased by increasing the speed with which the developer is cascaded across the xerographic surface.
  • Development electrodes may be used to provide solid area development and more efficient vibration imparting to the developer material.
  • the electrode consists of a grounded or biased member positioned as closely as possible to the xerographic surface to create an electric field in conjunction with the electrostatic charge pattern.
  • the electrode may comprise a plate or grid parallel to the xerographic surface and spaced therefrom.
  • the present invention provides novel apparatus for developing latent electrostatic charge pattern by vibrating a two-component developer material into a partial or total fluidized state in contact with the charge pattern for development thereof.
  • the apparatus of the present invention utilizes, a flexoral, or flexing, suspension for the bed and driver, the bed being coupled to-the driver by coil springs.
  • the flexing suspension of the bed and driver isolates the vibrations induced therein from the other elements of the reproducing system utilizing fluidized bed development.
  • the flexing suspension and coils springs are chosen to minimize the forces transmitted to the system during vibration of the bed.
  • FIG. 1 is a diagrammatic sectional view illustrating xerographic apparatus capable of carrying out the instant invention
  • FIG. 2 is a front view of development apparatus utilized in the apparatus shown in FIG. 1;
  • FIG. 3 is an upper right perspective of the vibrating elements utilized in the apparatus shown in FIG. I for imparting axial vibrations to the bed;
  • FIG. 4 is a schematic'representation of the drive system of the present invention.
  • developer material is brought into contact with a surface bearing latent electrostatic charge patterns in a manner such that the number of contacts between the material and the surface is increased over former techniques. Accordingly, a surface bearing the latent electrostatic charge pattern is moved through a bed of two-component developer in which the individual carrier particles are in a state of constant motion, and are impinged against the surface. Due to the constant motion of the developer particles, each incremental area of the surface is being continually contacted by different carrier beads and toner particles. The speed of agitation of the developer results in a substantial increase in the number of developer-charge pattern contacts for a given unit oftime.
  • a two-component developer is vibrated beneath a latent electrostatic charge pattern, or image.
  • the vibrations are so rapid as to cause the toner-holding carrier to fluidize, as that term is known in the art, or to become suspended in a fluidlike state wherein the individual particles are in constant motion.
  • the developer bed is then brought into contact with the surface to develop a latent electrostatic charge pattern.
  • the developer bed alternately, may be continuously in contact with the charged surface.
  • the developer composition may be of the conventional type as presently employed in commercial xerographic machines which use cascade techniques. Such a composition is defined, for example, in Walkup U.S. Pat. No. 2,618,551.
  • An example of such a composition comprises carrier beads of glass or steel which may be covered with and encased in a suitable coating, such as vinyl chloride, ethyl cellulose or phenyl formaldehyde which triboelectrically charges the toner upon contact.
  • the toner is usually a pigmented resinous material, or the like, which can be used to develop xerographic images.
  • the two-component developer is positioned and supported in an even and continuous layer over the surface of an arcuate plate, or tray, the plate then being vibrated transverse to the direction of movement of the member supporting the electrostatic charge pattern.
  • the surface having the latent electrostatic charge pattern thereon may then be positioned above the developer and plate so that the vibrated or fluidized developer bed will contact and develop the charge pattern.
  • the surface may be moved across the developer to thereby sequentially present new portions of the charge pattern for development.
  • techniques for than xerography may be utilized to deposit an electrostatic charge pattern on the surface of a support member, such as the electrostatic printer disclosed in U.S. Pat. No. 3,289,209.
  • the xerographic process will hereinafter be described.
  • the constant movement of the developer material within the fluidized bed causes the individual particles to continually move into and out of contact with the surface.
  • the transfer of the toner particles from their associated carrier beads to charge pattern areas occurs during this contact period.
  • the deposition of toner to the areas is physically caused either by the attraction of the charge pattern exceeding the attraction of the carrier for the toner or the toner being jarred loose from the carrier by the force of contact as it strikes the xerographic surface whereupon the charge in the image areas attract the loose toner.
  • the constant agitation or motion of the developer causes new or fresh developer to be continually brought into contact with the image-bearing surface and reduces the attraction of the carrier for the toner.
  • an automatic xerographic reproducing apparatus includes a xerographic surface formed in the shape ofa flexible belt 10, which is mounted to move in the direction indicated by the arrows to thereby cause the xerographic surface to sequentially pass through a plurality of processing stations.
  • the elements of this machine are all conventional in the xerographic art with the exception of the development station which is constructed to carry out the method ofthe instant invention.
  • the several xerographic processing stations in the path of movement of the xerographic surface may be described as follows:
  • a charging station A at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic belt
  • An exposure station B at which the light or radiation pattern of copy to be reproduced is projected onto the belt surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic charge pattern, or image, of the copy to be reproduced;
  • a development station C which forms the basis of the present invention, at which a xerographic developing material, including toner particles having an electrostatic charge opposite to that of the electrostatic latent image, are in contact with, or moved into contact with, the belt 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 powdered image is electrostatically transferred from the belt surface to a transfer material or a support surface;
  • a drum cleaning and discharge station E at which the belt surface is brushed to remove residual toner particles remaining thereon after image transfer, and at which the belt surface is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.
  • a xerographic surface in the form of a flexible belt 10 is supported for continuous motion through a xerographic development zone 11.
  • the surface is shown as a flexible belt trained over a plurality of rollers l2, l4 and 16, at least one of which is driven by any suitable power source, not shown, to drive the belt through the several processing stations.
  • any xerographic surface is equally suitable for carrying out the method of the instant invention, as for example, a drum or flat plate. If a flat plate is used, it may either be movable across the development zone or fixed with respect thereto.
  • the development station C illustrated in FlG. l is constructed of two major sections, a developer-vibrating assembly located at 30 (shown in detail in FIGS. 2 and 3) and a developer recirculation assembly 34.
  • the purpose of the developer-vibrating assembly is to impart vibrating motion to the two-component developer adjacent to the latent electrostatic image bearing surface.
  • the purpose of the developer recirculation assembly it to move developer to the input end of the developer-vibrating assembly after is has been moved beyond the developer-vibrating elements.
  • An arcuate plate 36 is positioned concentric with the belt 10 in an area vertically offset from the vertical centerline of the belt 10, to facilitate rapid movement of the developer through the development zone 111.
  • a suitable electrode grid 37 composed of a plurality of electrode wires 38, may be secured concentric with and between the belt 10 and arcuate plate 36.
  • the screen is grounded or provided with a bias from any suitable source of potential, not shown, to thus create an electrical field adjacent the image to aid in solid area development.
  • the axial electrodes shown are mounted in end plates 39 (FIG. 3) through suitable insulating barriers.
  • a plate 42 with a Lshaped cross section is provided in order to guide the vibrating developer in a return path towards the developer recirculation assembly 34. Plate 42 is stationary and is isolated from the vibrating bed.
  • the arcuate plate 36 is vibrated during operation of the xerographic apparatus for maintaining the developer in a fluidized state as described hereinabove.
  • the developer thus exhibits a movement down the longer leg 44 of the plate 42 towards the developer recirculation assembly 34 after reversing direction at the curved portion 46.
  • the developer recirculation assembly 34 is similar to the conventional type employed in most cascade development units.
  • a developer sump 48 is provided containing a supply of two-component developer for feeding into the development zone 11.
  • a bucket conveyor assembly comprising a plurality of buckets 50 mounted on a flexible endless belt 52 is held in position by two rollers 54 and 56.
  • Roller 54 is connected to a suitable source, not shown, for moving the buckets in a direction of the arrow.
  • the buckets act to raise the developer from the sump 48 to an elevated position for gravity feed to the development zone 11.
  • a toner dispenser 57 is provided for adding toner to the system to replace toner which has been depleted due to the development of images.
  • upper and lower plates 62 and 64 are also within the developer-recirculating assembly. These plates act as a stationary developer input chute 66 for the introduction of developer into the space between the arcuate plate 36 and belt 10.
  • resilient seals 67 and 69 are provided for coupling input chute 66 to the bed and return chute 71 to plate 44, respectively. Edge seals may be employed to effectively seal in the developer between J portion 46, upper plate 62 and belt 10.
  • the seal should preferably be made of a low-friction resilient material to minimize friction drag on the belt and bed drives.
  • the return and developer systems as described hereinabove are merely illustrative of such systems which may be utilized in the present invention. Other systems may be utilized, such as that disclosed in copending application Ser. No. 731,902.
  • the present invention is directed to novel means for vibrating the arcuate plate 36 and electrode grid 37 to fluidize the developer.
  • the development conveyor is continually bringing the twocomponent developer into the input chute for gravity-feeding developer to the development zone 11 above the arcuate plate 36 and between the electrode grid 37 and belt 10, the continuous bed vibrations reciprocating the developer between the plate and image-bearing surface.
  • the ground or bias on the vibrating electrode grid 37 establishes an electric field adjacent the image.
  • the vibrations of the grid assist in fluidizing the developer contacted thereby.
  • the grid allows the vibrated developer particles to freely move between the arcuate plate and image-bearing surface without interference therefrom.
  • arcuate plate 36 positioned immediately beneath a portion of the belt 10 is arcuate plate 36, shaped concentrically with belt 10.
  • the arcuate plate 36 is mounted adjacent opposite ends of the belt by mounting plates 39.
  • the lower portion of mounting plates 39 are attached to flexible metallic sheets, or flexors, 72, the lower ends of which are mounted to a base 74 by any suitable mounting mechanism.
  • vibrating electrode grid 37 is also positioned in the development zone 11 between the belt 10 and arcuate plate 36.
  • the grid is also mounted arcuately and concentric with both the belt and arcuate plate.
  • the opposite ends of the axial electrodes shown are mounted to mounting plates 39 through any suitable insulating barrier 78, such as polyethylene foam, plastic spacers or the like.
  • the grid 37 is adapted to be grounded or receive an electrical bias by a potential source not shown. Such electrical connection is adapted to render the grid a development electrode for the establishment of electric field adjacent the image for improved solid area development. It should be noted that development may take place without, the inclusion of the grid element.
  • Motion to the vibrational elements may be imparted, in the novel technique of the present invention, by an axially mounted electromagnetic driver 80, such as the V-50 voice coil type of linear vibrator manufactured by the Goodman Corporation.
  • the driver may be mounted off axis through suitable lever or bellcrank devices.
  • the electromagnetic driver is attached to flexible metallic sheets 76, the lower ends of which are mounted to base 74 by any suitable mounting mechanism.
  • the driving shaft 84 of the electromagnetic driver 80 is affixed to the mounting plate 39 at 88 either by riveting, bolting, or any other suitable mounting method.
  • the driver alternately may comprise a pneumatic driver actuated by a pulsating air supply, or the like.
  • the electromagnetic driver 80 is energized by applying pulsed current to a coil mounted adjacent shaft84 (not shown).
  • the current by known electromagnetic principles, causes an axial force to act on shaft 84.
  • coil springs 90 and 92 are mounted to shaft 84 by collars 94 and 96, respectively.
  • shaft 84 is driven in the direction indicated by arrow a," shaft 84 compressing or pushing spring 92 while pulling or placing spring 90 in tension.
  • the axial motion of shaft 84 is coupled to plate 39 by virtue of the mounting connection at 88.
  • the displacement of the arcuate plate containing the developer is readily controlled by limiting the current through the driver coil.
  • the suspension of plate 36 and driver 80 by using flexing means 72 and 76 isolates the vibrations introduced by the driver 80 from the rest of the xerographic apparatus.
  • the bed is vibrated at the resonant frequency of the mechanical system described hereinabove in order to minimize the force-power requirements necessary to fluidize the developer.
  • the advantages of using the driving system described hereinabove, other than low force-power requirements are low machine frame vibrations and noise and high reliability and life.
  • the suspension of the bed on the flexing means 72 provides axial and radial movement thereof, thereby providing radial as well as axial developer flow. This type of flow, characterized by an 8-shaped flow, provides additional developer-image contact areas, thereby producing higher quality images than heretofore possible.
  • the flexing sheets 72 and 76 are chosen for vibration isolation primarily, while the driver is operated at the resonant frequency of the driven system which in part comprises the flexing sheets and the coupling of coil springs 90 and 92.
  • the amplitude of vibration will be determined by the condition when the input energy to driver 80 equals or balances the dissipative energy due to hysteresis and interface damping. It should also be noted that there are no sliding parts in the developer system except for the seals.
  • the drive system described hereinabove may be schematically represented as a two-mass (static weight of the bed and electrode grid plus the dynamic weight of the developer when it is flowing through the bed and the weight of the driver), three-spring (flexors 72, 76, coil 90 an 92) system.
  • K represents the spring constant of flexing means 76
  • W represents the weight of driver 80
  • K 92 represents the spring constant of springs 90 and 92
  • W represents the static weight of the plate 36
  • K is the spring constant of flexing means 72
  • C is a dashpot representing the damping in the system
  • x and y are the directions in which the bed is to be vibrated.
  • the spring constants K and K preferably are small and are matched with their respective displacements, i.e., K FK Y.
  • the bed may be deflected to the left or right, represented by x and y, respectively, and, as is well known, when released will oscillate about its rest position with a predetermined period (or frequency and ever-decreasing amplitude due to the damping effect of the system as represented by dashpot C.
  • the resonant frequency of the system may be approximated by solution of the following second order differential equations:
  • the belt is set in motion by an conventional power source not shown. Concurrent with the movement of the belt, the vibration-imparting elements are set in motion by the activation of electromagnetic driver 80. At the same time, twocomponent develo er is thenlglravity fed through the development zone 11 an the grid lS given an electrical bias to thereby produce a development electrode field adjacent the image-bearing surface. The vibrations of the plate 36 and grid 37 thus cause the developer thereabove to fluidize itself for contacting and developing the image on the belt 10. After one or plural passes of the belt through the development zone 11, motions of the belt and vibrational elements may be stopped since development has been accomplished.
  • the driving system of the present in vention may be readily adapted to vibrate the fluidized bed in a direction substantially normal to or in the direction of the movement of the latent electrostatic image-bearing surface and still be within the purview of the present invention.
  • Apparatus for developing a latent electrostatic charge pattern formed on a support member with a two-component developer material comprising carrier particles and an electrostatically attractable powder comprising:
  • support means positioned adjacent to and beneath at least a portion of said support member for supporting a quantity of said developer material on the surface thereof;
  • first flexible means for suspending said support means
  • a vibratory member for producing vibrations when energized, said vibratory member positioned adjacent said support means and suspended by said second flexible suspending means;

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dry Development In Electrophotography (AREA)
US833459A 1969-06-16 1969-06-16 Developer for electrostatic images Expired - Lifetime US3613637A (en)

Applications Claiming Priority (1)

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US83345969A 1969-06-16 1969-06-16

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US3613637A true US3613637A (en) 1971-10-19

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US (1) US3613637A (enrdf_load_stackoverflow)
BE (1) BE752034A (enrdf_load_stackoverflow)
DE (1) DE2029697A1 (enrdf_load_stackoverflow)
FR (1) FR2052620A5 (enrdf_load_stackoverflow)
GB (1) GB1301157A (enrdf_load_stackoverflow)
NL (1) NL7008584A (enrdf_load_stackoverflow)
SE (1) SE358975B (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3953618A (en) * 1973-05-02 1976-04-27 Xonics, Inc. Electrostatic image developing process
DE2854614A1 (de) * 1977-12-20 1979-06-21 Konishiroku Photo Ind Putzvorrichtung fuer die trommel eines elektrophotographischen kopiergeraetes
US5742885A (en) * 1996-06-24 1998-04-21 Xerox Corporation Development system employing acoustic toner fluidization for donor roll

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU181524A1 (enrdf_load_stackoverflow) *
US2378025A (en) * 1942-05-09 1945-06-12 Carborundum Co Coating apparatus
US3254625A (en) * 1960-03-31 1966-06-07 Cecil W Armstrong Apparatus for producing a fluidized bed of pulverant material
US3357399A (en) * 1966-07-21 1967-12-12 Xerox Corp Combined fluidized bed and inverted cascade development apparatus
US3393663A (en) * 1966-07-21 1968-07-23 Xerox Corp Fluidizing electrode development apparatus
US3484265A (en) * 1966-07-21 1969-12-16 Xerox Corp Transversely reciprocating fluidized bed development method

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU181524A1 (enrdf_load_stackoverflow) *
US2378025A (en) * 1942-05-09 1945-06-12 Carborundum Co Coating apparatus
US3254625A (en) * 1960-03-31 1966-06-07 Cecil W Armstrong Apparatus for producing a fluidized bed of pulverant material
US3357399A (en) * 1966-07-21 1967-12-12 Xerox Corp Combined fluidized bed and inverted cascade development apparatus
US3393663A (en) * 1966-07-21 1968-07-23 Xerox Corp Fluidizing electrode development apparatus
US3484265A (en) * 1966-07-21 1969-12-16 Xerox Corp Transversely reciprocating fluidized bed development method

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3953618A (en) * 1973-05-02 1976-04-27 Xonics, Inc. Electrostatic image developing process
DE2854614A1 (de) * 1977-12-20 1979-06-21 Konishiroku Photo Ind Putzvorrichtung fuer die trommel eines elektrophotographischen kopiergeraetes
US5742885A (en) * 1996-06-24 1998-04-21 Xerox Corporation Development system employing acoustic toner fluidization for donor roll

Also Published As

Publication number Publication date
DE2029697A1 (de) 1972-02-17
FR2052620A5 (enrdf_load_stackoverflow) 1971-04-09
GB1301157A (en) 1972-12-29
SE358975B (enrdf_load_stackoverflow) 1973-08-13
NL7008584A (enrdf_load_stackoverflow) 1970-12-18
BE752034A (fr) 1970-12-16

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