US3825191A - Centrifugal mill for contact transfer electrostatic copier - Google Patents

Centrifugal mill for contact transfer electrostatic copier Download PDF

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Publication number
US3825191A
US3825191A US00295115A US29511572A US3825191A US 3825191 A US3825191 A US 3825191A US 00295115 A US00295115 A US 00295115A US 29511572 A US29511572 A US 29511572A US 3825191 A US3825191 A US 3825191A
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United States
Prior art keywords
developer
housing
liquid
cavity
recess
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00295115A
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English (en)
Inventor
I Smith
D Scroggs
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Savin Business Machines Corp
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Savin Business Machines Corp
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Filing date
Publication date
Application filed by Savin Business Machines Corp filed Critical Savin Business Machines Corp
Priority to US00295115A priority Critical patent/US3825191A/en
Priority to DE2347306A priority patent/DE2347306C3/de
Priority to IT29612/73A priority patent/IT993972B/it
Priority to FR7335746A priority patent/FR2202314A1/fr
Priority to JP48111583A priority patent/JPS4974035A/ja
Application granted granted Critical
Publication of US3825191A publication Critical patent/US3825191A/en
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
    • G03G15/10—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer
    • G03G15/104—Preparing, mixing, transporting or dispensing developer

Definitions

  • ABSTRACT A centrifugal impingement mill and developer supply system for an electrostatic copier using a developer made up of particles of tacky toner suspended in a carrier liquid in which a cylindrical spindle having a conical apex is provided with an annular radially extending vane located in the bulbous generally pearshaped cavity of a housing and is provided with a relatively broad cylindrical 'base disposed in relatively closely spaced relationship to the wall of a shallow cylindrical recess in the housing below the cavity to form , a vortex of developer liquid in the cavity above the recess and in which a first circulating path for developer containing relatively fine toner particles is provided from a point above the major diameter of the cavity to a developer applicator and back to an orifice adjacent to the top center of the housing and in which a second circulating path is provided for developer containing relatively coarse toner particles from a point adjacent to the major diameter of the cavity to the space
  • the. liquid developer comprises two prime components, a toner paste and a volatile, light hydrocarbon, carrier liquid.
  • the toner paste is an admixture of anadhesive resin, a pigment, solvents, and
  • tonerfcomponent is in the form of a paste-like organosol which is independently driven pumps maintain the fluid flow in each of the two circulation loops.
  • a deflocculating agent which tonerfcomponent is in the form of a paste-like organosol which is independently driven pumps maintain the fluid flow in each of the two circulation loops.
  • Emulsification is accomplished in the mill by subjecting insoluble in the carrier liqu'id.
  • the organosol or tonerpaste must be suspended in the carrier liquid.
  • the fine particles of toner paste migrate to the charged regions of the latent electrostatic image under the influence of the electric fields incident thereto.
  • the toner particles adhere to theimage areas of the photoconductive surface and arelatercontact-transferred to a copy medium for which they possess greater adherence affinity, thereby transferring the developed latent electrostatic image.
  • Excessdeveloper liquid is removed from the photoconductive surfaceand returned to a developer liquid trough by squeegee'rjollers, an air knife, or other liquid:
  • the structural arrangement of the mill is such that the rotor and stator vanes are located near the top of the mill housing and the emulsified liquid developer is drawn off from an opening at the bottom of the mill from which it is pumped to the developing zone. The entire mill assembly is located at a height above that of the developing zone.
  • the mill incorporates two principal deficiencies. In its operation the mill churned air bubbles into the developer liquid, which, owing to the rotor placement, remained trapped therein. These air bubbles impaired effective pumping of the developer liquid to the developing zone and deteriorated the liquids developing properties. It was also found that when not in use,excess liquid developer in the mill flowed'to the developing zone, where, by gravitational drainage, during the time the copier was idle, the toner particles tended to congeal and settle. Once agglomerated the mass of toner sediment could not entirely be pumped back to the mill for further mixing and agitation.
  • the application of Smith, et al., (II) discloses a milling device andlliquiddeveloper circulation system designed tosupply to the developing zone a tacky toner liquid developerin a well dispersed state.
  • the circulatory system employs two circulating loops; one from an intermediate toner supply tank to the developing zone and back, the other from the intermediate toner-supply tank to: an emulsifyingand mixing mill and back.
  • Our improved mill is arranged to receive liquid developer by gravitional drainage from the developing zone during periods of machine idleness. In this manner any toner particles which congeal and settle in the liquid developer do so in the mill cavity rather than in the developing zone tank.
  • the copy machine is again switched on the mill is activated and the sediment which has collected therein is emulsified and distributedthroughout the carrier liquid'in the mill cavity.
  • One object of our invention is to provide a continuous supply of extremely well mixed tacky toner liquid developer of correct composition, free from flocculates and air bubbles.
  • Another object of our invention is to provide a method of replenishing components of a tacky toner developer liquid as these components are depleted.
  • a further object of our invention is to restore the desirable properties of a tacky toner liquid developer after they have been lost during periods of copy machine idleness.
  • a still further object of our invention is to provide a wholly self-regulating developer supply system capable of continuously supplying a developer fluid of proper composition to a developing zone.
  • application instrumentalities are endless belts, polyurethane rollers, and spray devices.
  • Our centrifugal impingement mill performs three functions. It serves as a reservoir for the tacky toner liquid developer. It serves as a liquid developer emulsification apparatus. It serves as a pump which continuously circulates the liquid developer between the developing zone and the impingement mill. In this configuration well-mixed tacky toner liquid developer of proper composition is pumped up to the developing zone and then discharges back to the mill by gravitational drainage.
  • FIG. 1 is a diagrammatic view showing the developing station of an electrostatic copying apparatus employing a liquid developer and incorporating one embodiment of our invention.
  • FIG. 2 is a fragmentary sectional view of our centrifugal impingement mill used in our toner liquid developer circulation system.
  • FIG. 1 of the drawings we have shown a schematic view of our liquid developer circulation system and centrifugal impingement mill, in which a photoconductive surface 2 on a rotating drum 4 moves past a developing station indicated generally by the reference numeral 6.
  • the drum 4 and the developing station 6 are two components of a copy machine whose other components have been omitted from FIG. 1 since they do not per se form part of our invention.
  • the developing station 6 comprises an applicator tank 8 and overflow trough 10.
  • the developer liquid flows into the applicator tank 8 from a pipe 12 and is applied to the latent electrostatic image formed on the photoconductive surface by an application instrumentality (not shown) of any suitable type known to the art.
  • Excess liquid developer on the photoconductive surface is collected in the trough l and returns, by way of a pipe 14 to an aperture 15 in a centrifugal impingement mill, indicated generally by the reference character 16.
  • a centrifugal impingement mill indicated generally by the reference character 16.
  • the shaft 20 is positioned concentrically within a bulbous, pear-shaped mill housing 22 of spun aluminum, for instance, and is free to rotate therein on bearings 23.
  • the shaft 20 is suitably secured to a rotor 24 which forms the base of a concentrically mounted hollow spindle 28.
  • the stator body 26 supports a valve chamber 30 and a coarse fluid re-entrant chamber 32. These chambers extend through the stator body 26, opening into a space 33 between the cylindrical milling rotor 24 and the stator body.
  • a vortex forming vane 34 having the shape of a thin right circular annulus.
  • the cavity of the mill casing serves as a tacky toner liquid developer reservoir.
  • the mill continuously emulsifies and filters the liquid developer therein and pumps back to the developing station a liquid developer containing fine and evenly dispersed toner particles.
  • a container 36 holds a supply of toner paste or concentrate.
  • a threaded rod 40 or the like is adapted to be'screwed into one end 42 of container 36 to position a piston 43 to apply pressure to the toner concentrate which is conducted to chamber 30 by pipe 44.
  • the pipe 44 is normally closed by a valve 46 operated by a solenoid 47.
  • a valve stem normally engages a seat 48 to close the valve, and is actuated by an armature 49 of the solenoid 47 to which it is connected.
  • Operation of the solenoid 47 controls the admission of toner paste into the mill by lifting the stem 50 from its seat 48.
  • the operation of the solenoid 47 is controlled by a toner density monitoring system indicated generally by the reference numeral 52. When this occurs, the paste 38 from the valve chamber 30 flows into the space 33.
  • the spindle 28 and radially extending vane 34 rotate at about 2,800 revolutions per minute to form a vortex of developer liquid within the mill casing. Centrifugal forces within the fluid vortex accelerate the suspended toner particles outwardly toward the walls of the mill casing. The heavier toner particles and flocculates tend to collect near the walls of the mill casing while the lighter and finer toner particles tend to remain close to the spindle.
  • the walls of the mill casing are especially shaped to take advantage of the selective filtration process performed by the centrifugal forces within the vortex.
  • the mill casing is pear shaped, bulging outwardly in the vicinity of the vane 34 and tapering inwardly toward the top.
  • An emission aperture is placed at a point above the major diameter of the mill, where the walls of the mill casing slope inwardly toward the conical apex of the spindle to tap the portion of the fluid vortex nearer the spindle which contains the finer and lighter toner particles. This point may be empirically determined after parameters such as the liquid developer's composition, the rotational speed of the vane, and the vanes diameter have been set.
  • the situs of the emission aperture reflects a balance between fineness of toner particles tapped and the pressure needed to drive this portion of the liquid developer through the developer feed pipe 12. While finer toner particles accumulate near narrower mill radii, vortex pressure decreases with decreasing radius. The vortex pressure pumps this optimum tacky toner emulsion to the developing station through the pipe 12.
  • a coarse toner particle outlet 53 to tap that portion of the fluid vortex containing the heavier toner particles and flocculates.
  • These heavier particles are driven by vortex generated pressure through a coarse return pipe 56 which communicates with the re-entrant chamber 32 in the stator body 26.
  • the heavier particles entering the chamber 32 are admitted to the milling zone 54 to be reground by shearing forces generated therein and sprayed back into the fluid volume in the mill cavity.
  • This jet of highly emulsified, fine toner particles breaks up and scatters toner sediment which may have congealed in the vicinity of the rotor during periods of machine idleness.
  • This sediment is thrust toward the coarse outlet 53 by vortex generated pressure and enters the coarse return pipe 56 to be reground and sprayed back into the fluid body in the mill cavity.
  • our invention causes coarse toner particles and flocculates to be continuously removed from the fluid vortex within the mill and recirculated to the milling zone between the rotor and stator where they are reground and injected to the fluid body in a finer state.
  • the tacky toner liquid developer will uniformly and completely transfer to the copy medium with which it is contacted, leaving no residue on the photoconductor surface.
  • a tacky toner liquid developers transfer properties depart from i this optimum state over many milling cycles and the toner begins to gel. The overmilled developer loses cohesiveness and becomes increasingly adhesive.
  • our impingement mill serves as a reservoir for the light hydrocarbon carrier liquid with which the toner paste is emulsified.
  • the cavity of the mill 16 is normally filled with carrier liquid to a height slightly above the conical apex of the spindle 28.
  • the motor 18 When the electrostatic copieris energized, the motor 18 operates to rotate the cylindricalmilling rotor 24 and the vane 34. The fluid vortex formed by this rotation begins-to pump the liquid developer to the developing station in the direction of arrow G, by way of the pipe 12.
  • the coarse toner particle filtration circuit is activated, as explained hereinabove, and a jet of fine toner particles, moving upwardly in the direction of arrows B and C, from the emulsification zone, breaks up any toner sediment which may have accumulated above the rotor during periods of machine idleness.
  • the discharged liquid developer, depleted in toner particles returns from the overflow trough of the developing station to the mill cavity by way of the pipe 14 and the inlet in the direction of the arrow H in FIG. 2.
  • Bubbles which may form in the liquid developer fluid are displaced upwardly to the air region above the fluid meniscus and escape to the atmosphere as explained hereinabove, through the air escape orifice 58, arrow F in FIG. 2.
  • centrifugal impingement mill is adapted to overcome the deterioration of the transfer properties of the liquid developer resulting from overmilling.
  • a tacky toner liquid developer exhibits great cohesiveness and anti-fracture strength, while exhibitmay, within limits, reduce the speed of rotation of the rotor and the spindle-vane assembly.
  • our invention has eliminated the need for the pumps which maintained the fluid flow in those loops.
  • Our centrifugal impingement mill serves as the fluid storage tank and provides the pumping action needed to maintain fluid flow in a single circulation loop.
  • our centrifugal impingement mill may be used in the dual circulation loop system or in a multi-loop circulation system and still achieve the objective of providing an extremely well mixed liquid developer.
  • the motor 18 may be arranged in a number of different configurations, to impart motion to the cylindrical milling rotor 24 and the vane 34.
  • the motor may be located above the mill to directly drive the cylindrical milling rotor 24 and the vane 34 through a shaft secured to the spindle at its apex, or the motor may rotate the assembly from a more remote location, through appropriately arranged gear chains.
  • a bulbous cavity having a major diameter
  • milling means adapted to exert shear forces on developer liquid fed thereto
  • said milling means includes a cylindrical recess in said housing below said cavity, a cylindrical rotor portion disposed in said recess in closely spaced relationship thereto and means for driving said rotor to exert shear forces on said developer liquid in the space between said rotor and the wall of said recess, said conducting means conducting developer liquid from said housing at a location adjacent to said major diameter to the space between said rotor and said recess wall.
  • Apparatus for supplying liquid developer made up of tacky toner particles suspended in a carrier liquid to the developer applicator unit of an electrostatic copying machine including in combination, a housing forming a bulbous cavity having a major diameter and a cylindrical recess below said cavity, a rotor in said housing, said rotor comprising a vortex forming portion located in said cavity and a cylindrical portion in said recess in closely spaced relationship to the wall thereof, means for driving said rotor to cause said vortex forming portion to form a vortex of developer liquid in said cavity and to cause said cylindrical portion to exert shear forces on said developer liquid in the spaces between the cylindrical portion and the wall of the recess, means for conducting liquid from said vortex to said developer unit and back to said housing, and means for conducting developer from said housing at a location adjacent to said major diameter to the space between said cylindrical rotor portion and the wall of said recess.
  • Apparatus as in claim 4 including means providing communication between the interior of said housing and the surrounding space.
  • Apparatus as in claim 4 including means for introducing concentrated toner into the space between the cylindrical rotor portion and the wall of said recess.
  • Apparatus as in claim 4 including means mounting said housing below said applicator unit.
  • a centrifugal impingement mill and developer supply system for an electrostatic copier using a developer made up of particles of tacky toner suspended in a carrier liquid including in combination, a cylindrical spindle having a conical apex, radially extending vane and broad cylindrical rotor base, a stator formed with a cylindrical recess disposed at the bottom of a cavity within a bulbous, generally pear-shaped housing and forming a narrow space between said rotor base and said stator, means for feeding toner material into said space, means for moving said rotor base and said spindle relative to said stator to apply shearing forces to material in said space and to form a vortex in liquid developer contained in said cavity, means forming a first circulating path for developer containing predominantly fine toner particles from a point above the major diameter of said housing to a developer applicator unit and back to an orifice adjacent the top center of said housing, and means forming a second circulating path for developer containing predominantly coarse toner particles from a point
  • said housing forms a surface symmetric about a longitudinal axis and has a radius which varies along the longitudinal direction of said axis to extend outwardly in the vicinity of said vane and taper inwardly toward said conical apex and said rotor base of said spindle.
  • said housing contains an air-escape orifice at a location on its surface above the meniscus of the developer fluid contained therein, an emission orifice above the major diameter of said housing through which said developer containing predominantly flne toner particles enters said first circulating path, and a coarse outlet on the portion of its surface adjacent the major axis of said housing through which said developer containing predominantly coarse toner particles enters said second circulating path.
  • said space forming means comprises disposing said cylindrical rotor base in a relatively close spaced relationship with walls of said recess formed in said stator, said directing means comprising a toner valve chamber in said stator opening on said space through which toner concentrate is admitted and a re-entrant chamber in said stator opening on said space through which liquid developer containing predominantly coarse toner particles is admitted from said second circulating path.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Wet Developing In Electrophotography (AREA)
  • Liquid Developers In Electrophotography (AREA)
US00295115A 1972-10-05 1972-10-05 Centrifugal mill for contact transfer electrostatic copier Expired - Lifetime US3825191A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US00295115A US3825191A (en) 1972-10-05 1972-10-05 Centrifugal mill for contact transfer electrostatic copier
DE2347306A DE2347306C3 (de) 1972-10-05 1973-09-20 Verfahren und Einrichtung zum Inumlaufbringen von Entwicklerflüssigkeit
IT29612/73A IT993972B (it) 1972-10-05 1973-10-01 Mulino centrifugo per una macchina copiatrice elettrostatica a trasfe rimento per contatto
FR7335746A FR2202314A1 (enExample) 1972-10-05 1973-10-05
JP48111583A JPS4974035A (enExample) 1972-10-05 1973-10-05

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US00295115A US3825191A (en) 1972-10-05 1972-10-05 Centrifugal mill for contact transfer electrostatic copier

Publications (1)

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US3825191A true US3825191A (en) 1974-07-23

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US00295115A Expired - Lifetime US3825191A (en) 1972-10-05 1972-10-05 Centrifugal mill for contact transfer electrostatic copier

Country Status (5)

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US (1) US3825191A (enExample)
JP (1) JPS4974035A (enExample)
DE (1) DE2347306C3 (enExample)
FR (1) FR2202314A1 (enExample)
IT (1) IT993972B (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5530533A (en) * 1995-03-06 1996-06-25 Xerox Corporation High solids toner redispersion

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5530533A (en) * 1995-03-06 1996-06-25 Xerox Corporation High solids toner redispersion

Also Published As

Publication number Publication date
JPS4974035A (enExample) 1974-07-17
DE2347306A1 (de) 1974-04-11
DE2347306B2 (de) 1975-03-13
IT993972B (it) 1975-09-30
FR2202314A1 (enExample) 1974-05-03
DE2347306C3 (de) 1975-10-30

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