US3257224A - Method and apparatus for developing electrostatic images - Google Patents

Method and apparatus for developing electrostatic images Download PDF

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US3257224A
US3257224A US247025A US24702562A US3257224A US 3257224 A US3257224 A US 3257224A US 247025 A US247025 A US 247025A US 24702562 A US24702562 A US 24702562A US 3257224 A US3257224 A US 3257224A
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roller
developer
trough
toner
magnetic
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US247025A
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Jons Kurt
Wolfinger Arthur
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Azoplate Corp
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Azoplate 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
    • G03G15/09—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

Definitions

  • the developers normally used in electrophotography consist of a mixture of finely divided resinous toner and a carrier for the toner of somewhat larger particle size than the toner.
  • the carrier is often of magnetizable material, e.g. iron filings, in order to enable the developer to be applied with the aid of a rotating magnetic roller to the surface of a latent electrostatic image.
  • the magnetic roller which may be a permanent magnet or may be magnetized by an electric current, dip into developer powder contained in a trough beneath the roller.
  • the toner is attracted electrostatically from the magnet to the photoconductive coating of the electrophotographic material and a visible image is formed.
  • the developer, depleted in toner is returned to the trough as the magnetic roller rotates.
  • the iron filings always come to rest at the same place, namely near the point at which renewed magnetization of the poles occurs so that the mixing operation in the trough, which can be carried out at a limited speed only and which is intended to load the iron filings with new toner, cannot take place sufiiciently rapidly.
  • the roller therefore continually picks up the toner-depleted iron filings which have just been dropped as a result of the demagnetization.
  • the present invention provides an apparatus for developing latent electrostatic images comprising a trough to contain a developer mixture of iron filings and toner powder, an agitator in the trough, an electromagnetically excited iron roller for picking up developer from the trough and transferring it to the electrophotographic material to be developed, the iron roller being made of up of rotor plates having a number of windings to which exciting current is supplied intermittently, being cut off once in every revolution of the roller and a covering of synthetic plastic 3,257,224 Patented June 21, 1956 material, and a deflector plate which coacts with the portion of the roller traveling away from the electrophotographic material and towards the developer contained in the trough to deflect towards the wall of the trough developer shed by the roller while the current is cut off.
  • the laminations of the roller consists of relatively thin soft iron sheets placed side by side with layers 'of insulating material between them.
  • the shape of these plates corresponds to the cross section of the intended roller. If the notches provided for the windings are even in number, particularly good results can be obtained.
  • the covering on the roller mayconsist of any suitable insulating plastic which is solid at normal temperatures.
  • suitable plastics are thermoplastics, such as polyolefins, e.g. polyethylene and polypropylene, polyvinyl compounds such as polyvinyl chloride, polyamides and polyesters.
  • thermosetting resins e.g. phenolformaldehyde resins.
  • plastics such as those used for insulating purposes in transformers; they are described, for example, in the handbook of Messrs. lSchgamm, Lackund, Wegrik AG, Elektro-Isolierac e.
  • the plastic coating can be applied by placing the magnetic roller in a mold, the gap between the inner Walls of mold and the surface of the magnetic roller being greater than the thickness of the plastic coating which is to be produced on the surface of the roller.
  • the intermediate spaces are now filled with a substance which contains unhardened components of a resin mixture together with a hardener. The whole is then allowed to 'stand for 20-30 hours, during which time the plastic hardens completely. After removing the roller from the mold, it is advantageous for'the surface of the plastic coating to be evened and smoothed by turning.
  • the plastic covering may also be applied to the roller by painting on a mixture of the plastic substance and a hardener.
  • the thickness of the painted coating is advantageously considerably greater than the thickness finally required.
  • the surface of the plastic coating is again finished by turning and polishing.
  • Plastic coatings, particularly thermoplastic coatings can also be applied to the roller surface in the form of ready made foils by wrapping and, where necessary, fusing.
  • the thickness of the plastic coating on the surface of the electromagnetic roller is generally between 0.2 and 1.0 mm. preferably 0.4-0.5 mm., but lesser or greater thicknesses can also be successfully used.
  • the surface of the plastic coating on the magnetic roller may be made electrically conducting and may be provided with a bias voltage with respect to the surface of the photoconductive layer of the electrophotographic material or it may be grounded. This is particularly advantageous in the case of the development of latent electrostatic images which, because of inadequate exposure, have a residual charge in the image-free parts.
  • the surface can, for example, be made conductive by treatment with a dispersion of silver particles in a suitable dispersion agent, e.g. the so-called Leitsilber (conducting silver), or it can be .coated with metal. Good results are also obtained by the application of a thin metal foil to the roller.
  • a suitable dispersion agent e.g. the so-called Leitsilber (conducting silver)
  • Leitsilber conducting silver
  • the deflector plate extends over the whole width of the electromagnetic roller.
  • the distance of the deflector plate from the surface of the roller should be kept as small as possible.
  • the length of the surface of the deflector plate over which the toner-depleted carrierruns should be as great as possible.
  • the deflector plate should discharge the carrier near to the wall of the trough.
  • the deflector plate can be joined underneath with the normally used securing devices to the wall of the vessel.
  • the apparatus may include a container for toner powder adjacent the trough and means for periodically delivering measured quantities of toner powder from the container to the trough.
  • FIGURE 1 is a transverse section through the developing apparatus
  • FIGURE 2 is a plan view
  • FIGURE 3 is a longitudinal section through the developing apparatus
  • FIGURE 4 shows the current supply member in crosssection
  • FIGURE 4a shows the current supply member in plan view.
  • the apparatus includes an electromagnetically excited roller 1 having a shaft 2 which is journaled in bearings 3 and 4 and is driven by the gears 5, 6 and 7.
  • the windings 9 of the roller 1 receive current from a source, not shown, of direct current via individual slip rings 10. 1
  • the roller 1 has twelve grooves 9' containing six separate windings which are excited by means of six slip rings 10 which coact with the brushes 26.
  • the roller 1 also has a coating 11 of synthetic plastic material. Between points 12 and 13, the slip rings 10 are provided with means for interrupting the current.
  • the roller rotates anticlockwise as viewed in FIGURE 4 and, as soon as the windings 9 have passed the point 13, they are deprived of current.
  • the developer carried by the roller is then dropped off and is deflected by a deflector plate 14 to the outer edge of the developer trough.
  • the discarded developer works its way very slowly back from the outer edge of the developer trough 14' to the agitator 15 in the trough and is taken up by the agitator and, after intensive mixing, passed to the point 12, at which magnetization of the roller recommences, and is there taken up by the roller.
  • the plastic coating 11 on the magnetic roller 1 ensures that after the current has been switched off at the point 13 the developer will not remain attracted by residual magnetism.
  • the trough is replenished with toner in a simple manner and without dust by the following mechanism:
  • a container 17 (FIG. 3) contains a certain quantityof toner for purposes of replenishment.
  • the trough is replenished with toner from the container 17 by dosing plungers 18.
  • End plates 19 on the plungers 18 normally close the feed opening 20 in the wall of the container 17 and the plungers carry sealing sleeves 21.
  • the plungers, which are fitted with return springs 24, are actuated by rocker arms 22 from a motordriven eccentric 23, which is driven at a speed appropriate to requirements.
  • the toner in the container 17 is agitated by a vane 25 which is vibrated by a rocker magnet.
  • Apparatus for developing latent electrostatic images comprising a trough adapted to contain a developer having a magnetic component, a rotatable electrically magnetizable roller mounted in the trough, the roller having a plurality of separate windings and an insulating layer on the roller surface, means for supplying and interrupting an electric current to at least one of the windings during rotation of the roller to thereby successively magnetize and demagnetize portions of the roller surface, and defleeting means mounted adjacent the roller.
  • Apparatus according to claim 1 including a container adapted to contain toner mounted adjacent the trough and means for delivering measured quantities of toner to the trough.
  • a process for applying a developer to a latent electrostatic image which comprises electrically generating a magnetic field in portions of a surface of a rotatable applicator submerged in a body of developer having a magnetic component, rotating the said portions of the surface carrying developer thereon into contact with the latent electrostatic image, rotating the said portions of the surface out of contact with the electrostatic image and interrupting the electric current, thereby eliminating the magnetic field from said portions of said surface, and passing excess developer from said portions of said surface back into the body of developer at a point remote from the initial position of the developer in the body.

Description

June 21, 1966 K. JONs ETAL 3,257,224
METHOD AND APPARATUS FOR DEVELOPING ELECTROSTATIC IMAGES Filed Dec. 26, 1962 5 Sheets-Sheet 1 FIG. I
FIG. 2
INVENTORS KURT .16 s ARTHUR w LFINGER k z- M ATTOR EY METHOD AND APPARATUS FOR DEVELOPING ELECTROSTATIC IMAGES Filed Dec. 26, 1962 5 Sheets-Sheet 2 FIG?) INVENTORS KURT J5N. ARTHUR WOLFINGER BY J ORNEY June 21, 1966 oNs ETAL 3,257,224
METHOD AND APPARATUS FOR DEVELOPING ELECTROSTATIC IMAGES Filed Dec. 26, 1962 5 Sheets-Sheet 5 INVENTORS KURT J6N, ARTHUR w LFlNGER BY aw... Z.
TTORNEY United States Patent '0 9 Claims. Ci. 117 17.5)
The developers normally used in electrophotography consist of a mixture of finely divided resinous toner and a carrier for the toner of somewhat larger particle size than the toner. The carrier is often of magnetizable material, e.g. iron filings, in order to enable the developer to be applied with the aid of a rotating magnetic roller to the surface of a latent electrostatic image.
The magnetic roller, which may be a permanent magnet or may be magnetized by an electric current, dip into developer powder contained in a trough beneath the roller. The iron filings, carrying the toner on their surfaces, adhere in brush-like formation to the magnetic poles of the roller and are applied in this form by the rotation of the roller to the surface of a charged electrophotographic material which has been exposed imagewise and is traversed over the roller. The toner is attracted electrostatically from the magnet to the photoconductive coating of the electrophotographic material and a visible image is formed. The developer, depleted in toner, is returned to the trough as the magnetic roller rotates.
This procedure has the disadvantage that the iron filings adhering to the roller become progressively depleted in toner and, as a result, the quality of the developed image progressively deteriorates.
It has accordingly been proposed to release the iron filings from an electromagnetically excited roller by periodically switching off the exciting current so that the roller can be charged anew with fresh toner from the trough in which the developer is agitated to keep it in constant movement. As such complete interruption of the exciting current produces an uneven developing effect, it has also been proposed to switch off the exciting current at the magnetic poles only which are on the circumference of Q the semicircle between the point of contact of the developer with the electrophotographic' material and the point at which the roller dips into the developer in the trough. This proposal also fails to give the desired results because a certain residual magnetism persists at the magnetic poles after the exciting current has been switched off, so that the developer powder cannot drop otf completely and therefore renewal of the developer takes place to a limited extent only.
Moreover, the iron filings always come to rest at the same place, namely near the point at which renewed magnetization of the poles occurs so that the mixing operation in the trough, which can be carried out at a limited speed only and which is intended to load the iron filings with new toner, cannot take place sufiiciently rapidly. The roller therefore continually picks up the toner-depleted iron filings which have just been dropped as a result of the demagnetization.
The present invention provides an apparatus for developing latent electrostatic images comprising a trough to contain a developer mixture of iron filings and toner powder, an agitator in the trough, an electromagnetically excited iron roller for picking up developer from the trough and transferring it to the electrophotographic material to be developed, the iron roller being made of up of rotor plates having a number of windings to which exciting current is supplied intermittently, being cut off once in every revolution of the roller and a covering of synthetic plastic 3,257,224 Patented June 21, 1956 material, and a deflector plate which coacts with the portion of the roller traveling away from the electrophotographic material and towards the developer contained in the trough to deflect towards the wall of the trough developer shed by the roller while the current is cut off.
By means of this apparatus, the above-mentioned disadvantages are eliminated. The residual magnetism on the magnetic poles during the period in which the current is switched off can no longer hold the iron filings of the developer because of the plastic coating. The developer powder shed by the roller is deflected by the deflector plate to a place remote from the pick-up point of the electromagnetic roller, so that it can be fully recharged with toner powder by the agitator in the trough before it is again taken up by the electromagnetic roller. Rotor plates are understood as components such as are used in the electrical industry for the production of rotors in electric motors.
The laminations of the roller consists of relatively thin soft iron sheets placed side by side with layers 'of insulating material between them. The shape of these plates corresponds to the cross section of the intended roller. If the notches provided for the windings are even in number, particularly good results can be obtained. When the individual rotor blades are placed together along the rotational axis and the poles are wound, the magnetic roller to be used as provided by the invention is formed. Any desired length may be produced.
The covering on the roller mayconsist of any suitable insulating plastic which is solid at normal temperatures. Examples of suitable plastics are thermoplastics, such as polyolefins, e.g. polyethylene and polypropylene, polyvinyl compounds such as polyvinyl chloride, polyamides and polyesters. Good results are also obtained with thermosetting resins, e.g. phenolformaldehyde resins. Particularly favorable results are obtained with plastics such as those used for insulating purposes in transformers; they are described, for example, in the handbook of Messrs. lSchgamm, Lackund, Farbenfabrik AG, Elektro-Isolierac e.
The plastic coating can be applied by placing the magnetic roller in a mold, the gap between the inner Walls of mold and the surface of the magnetic roller being greater than the thickness of the plastic coating which is to be produced on the surface of the roller. The intermediate spaces are now filled with a substance which contains unhardened components of a resin mixture together with a hardener. The whole is then allowed to 'stand for 20-30 hours, during which time the plastic hardens completely. After removing the roller from the mold, it is advantageous for'the surface of the plastic coating to be evened and smoothed by turning. i
The plastic covering may also be applied to the roller by painting on a mixture of the plastic substance and a hardener. In such cases, the thickness of the painted coating is advantageously considerably greater than the thickness finally required. After hardening out, the surface of the plastic coating is again finished by turning and polishing. Plastic coatings, particularly thermoplastic coatings, can also be applied to the roller surface in the form of ready made foils by wrapping and, where necessary, fusing. v
The thickness of the plastic coating on the surface of the electromagnetic roller is generally between 0.2 and 1.0 mm. preferably 0.4-0.5 mm., but lesser or greater thicknesses can also be successfully used.
The surface of the plastic coating on the magnetic roller may be made electrically conducting and may be provided with a bias voltage with respect to the surface of the photoconductive layer of the electrophotographic material or it may be grounded. This is particularly advantageous in the case of the development of latent electrostatic images which, because of inadequate exposure, have a residual charge in the image-free parts.
The surface can, for example, be made conductive by treatment with a dispersion of silver particles in a suitable dispersion agent, e.g. the so-called Leitsilber (conducting silver), or it can be .coated with metal. Good results are also obtained by the application of a thin metal foil to the roller.
The deflector plate extends over the whole width of the electromagnetic roller. The distance of the deflector plate from the surface of the roller should be kept as small as possible. The length of the surface of the deflector plate over which the toner-depleted carrierruns should be as great as possible. The deflector plate should discharge the carrier near to the wall of the trough. The deflector plate can be joined underneath with the normally used securing devices to the wall of the vessel.
The apparatus may include a container for toner powder adjacent the trough and means for periodically delivering measured quantities of toner powder from the container to the trough.
One embodiment of developing apparatus according to the invention will now be described in more detail, by way of example, with reference to the accompanying diagrammatic drawings, in which:
FIGURE 1 is a transverse section through the developing apparatus,
FIGURE 2 is a plan view,
FIGURE 3 is a longitudinal section through the developing apparatus,
FIGURE 4 shows the current supply member in crosssection, and
FIGURE 4a shows the current supply member in plan view.
As shown in FIGURES 1 and 2, the apparatus includes an electromagnetically excited roller 1 having a shaft 2 which is journaled in bearings 3 and 4 and is driven by the gears 5, 6 and 7. The windings 9 of the roller 1 receive current from a source, not shown, of direct current via individual slip rings 10. 1
As shown in FIGURES 3, 4 and 4a, the roller 1 has twelve grooves 9' containing six separate windings which are excited by means of six slip rings 10 which coact with the brushes 26. The roller 1 also has a coating 11 of synthetic plastic material. Between points 12 and 13, the slip rings 10 are provided with means for interrupting the current. The roller rotates anticlockwise as viewed in FIGURE 4 and, as soon as the windings 9 have passed the point 13, they are deprived of current. The developer carried by the roller is then dropped off and is deflected by a deflector plate 14 to the outer edge of the developer trough. The discarded developer works its way very slowly back from the outer edge of the developer trough 14' to the agitator 15 in the trough and is taken up by the agitator and, after intensive mixing, passed to the point 12, at which magnetization of the roller recommences, and is there taken up by the roller. The plastic coating 11 on the magnetic roller 1 ensures that after the current has been switched off at the point 13 the developer will not remain attracted by residual magnetism.
The trough is replenished with toner in a simple manner and without dust by the following mechanism:
A container 17 (FIG. 3) contains a certain quantityof toner for purposes of replenishment. As the toner is consumed, the trough is replenished with toner from the container 17 by dosing plungers 18. End plates 19 on the plungers 18 normally close the feed opening 20 in the wall of the container 17 and the plungers carry sealing sleeves 21. The plungers, which are fitted with return springs 24, are actuated by rocker arms 22 from a motordriven eccentric 23, which is driven at a speed appropriate to requirements. The toner in the container 17 is agitated by a vane 25 which is vibrated by a rocker magnet.
It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.
What is claimed is:
1. Apparatus for developing latent electrostatic images comprising a trough adapted to contain a developer having a magnetic component, a rotatable electrically magnetizable roller mounted in the trough, the roller having a plurality of separate windings and an insulating layer on the roller surface, means for supplying and interrupting an electric current to at least one of the windings during rotation of the roller to thereby successively magnetize and demagnetize portions of the roller surface, and defleeting means mounted adjacent the roller.
2. Apparatus according to claim 1 in which the insulating layer is a plastic material.
3. Apparatus according to claim 1 including a container adapted to contain toner mounted adjacent the trough and means for delivering measured quantities of toner to the trough.
4. Apparatus according to claim 1 in which the roller comprises a plurality of rotor plates.
5. Apparatus according to claim 1 in which the roller 15 iron.
' 6. Apparatus according to claim 1 in which the deflecting means is a plate.
7. Apparatus according to claim 1 in which the trough also contains means for agitating the developer.
8. A process for applying a developer to a latent electrostatic image which comprises electrically generating a magnetic field in portions of a surface of a rotatable applicator submerged in a body of developer having a magnetic component, rotating the said portions of the surface carrying developer thereon into contact with the latent electrostatic image, rotating the said portions of the surface out of contact with the electrostatic image and interrupting the electric current, thereby eliminating the magnetic field from said portions of said surface, and passing excess developer from said portions of said surface back into the body of developer at a point remote from the initial position of the developer in the body.
9. A process according to claim 8 in which toner is intermittently added to the body of developer.
References Cited by the Examiner UNITED STATES PATENTS 404,465 6/1889 Bradley 310-46 X 500,400 6/1893 Lange.
673,980 5/1901 Engelhardt 310-46 1,048,223 12/1912 Stein 209-223 1,177,981 4/1916 Wright 209-219 X 1,362,072 12/ 1920 Arnold 209-219 1,371,301 3/1921 Converse 209-219 1,449,371 3/1923 Apple 310-45 X 2,449,021 9/1948 Stahl.
2,711,249 6/1955 Laurila 209-219 2,779,306 1/1957 Dunn 11717.5 X 2,832,311 4/1958 Byrne 118-637 2,844,489 7/1958 Gemmer 117-22 2,896,101 7/1959 Laskin 310-171 2,904,000 9/1959 Fisher et al 118-637 2,956,487 10/1960 Giaimo 117-17.5 X 2,975,758 3/1961 Bird 118-637 2,992,733 7/1961 Buns et al 209-219 3,003,462 10/1961 Streich 118-637 3,028,266 4/1962 Larsh 117-232 3,028,708 4/1962 Vaughan et al 209-219 3,040,704 6/1962 Bliss 118-637 3,081,737 3/1963 Frantz et al 1l717.5 X 3,088,386 5/1963 Sugarman 118-637 X 3,098,765 7/1963 Keller et al 117-17.5 X 3,152,924 10/1964 Wanielista et al. 117-17.5 X
WILLIAM D. MARTIN, Primary Examiner.
G. L. HUBBARD, Assistant Examiner.

Claims (1)

  1. 8. A PROCESS FOR APPLYING A DEVELOPER TO A LATENT ELECTROSTATIC IMAGE WHICH COMPRISES ELECTRICALLY GENERATING A MAGNETIC FIELD IN PORTIONS OF A SURFACE OF A ROTATABLE APPLICATOR SUBMERGED IN A BODY OF DEVELOPER HAVING A MAGNETIC COMPONENT, ROTATING THE SAID PORTIONS OF THE SURFACE CARRYING DEVELOPER THEREON INTO CONTACT WITH THE LATENT ELECTROSTATIC IMAGE, ROTATING THE SAID PORTIONS OF THE SUR-
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US3318284A (en) * 1964-01-30 1967-05-09 Hitachi Ltd Apparatus for developing electrostatic images of records
US3574301A (en) * 1969-04-02 1971-04-13 Xerox Corp Developing apparatus
US3996892A (en) * 1975-02-24 1976-12-14 Xerox Corporation Spatially programmable electrode-type roll for electrostatographic processors and the like
US3998185A (en) * 1975-02-03 1976-12-21 Xerox Corporation Microfield donors with toner agitation and the methods for their manufacture
US4017648A (en) * 1975-02-03 1977-04-12 Xerox Corporation Toner agitation through microfield donor
US4086873A (en) * 1974-07-09 1978-05-02 Konishiroku Photo Industry Co., Ltd. Electrophotographic developing device incorporating a developing electrode having an insulation layer on its surface
US5063412A (en) * 1990-09-26 1991-11-05 Xerox Corporation Development apparatus using an electromagnet to prevent development in the non-operative mode
US5289240A (en) * 1993-05-20 1994-02-22 Xerox Corporation Scavengeless developer unit with electroded donor roll
US5360940A (en) * 1993-07-14 1994-11-01 Xerox Corporation Scavengeless two component development with an electroded development roll
EP0691586A1 (en) 1994-07-05 1996-01-10 Xerox Corporation Development apparatus having an adjustable width development nip
US5500969A (en) * 1994-10-24 1996-03-26 Xerox Corporation Dual polarity commutated roll elctrostatic cleaner with acoustic transfer assist
US5570169A (en) * 1995-09-25 1996-10-29 Xerox Corporation Donor rolls with modular commutation
US5589917A (en) * 1995-09-25 1996-12-31 Xerox Corporation Donor rolls with magnetically coupled (Transformer) commutation
US5592271A (en) * 1996-01-11 1997-01-07 Xerox Corporation Donor rolls with capacitively cushioned commutation
US5594534A (en) * 1996-01-11 1997-01-14 Xerox Corporation Electroded doner roll structure incorporating resistive network
US5600418A (en) * 1995-09-25 1997-02-04 Xerox Corporation Donor rolls with exterior commutation
US5614995A (en) * 1995-09-05 1997-03-25 Xerox Corporation Electroded donor roll having robust commutator contacts
US5745827A (en) * 1997-03-31 1998-04-28 Xerox Corporation Bundled steel wire SED communicator secondary cores

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US3687106A (en) * 1969-07-11 1972-08-29 Xerox Corp Donor apparatus and method

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Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3318284A (en) * 1964-01-30 1967-05-09 Hitachi Ltd Apparatus for developing electrostatic images of records
US3574301A (en) * 1969-04-02 1971-04-13 Xerox Corp Developing apparatus
US4086873A (en) * 1974-07-09 1978-05-02 Konishiroku Photo Industry Co., Ltd. Electrophotographic developing device incorporating a developing electrode having an insulation layer on its surface
US3998185A (en) * 1975-02-03 1976-12-21 Xerox Corporation Microfield donors with toner agitation and the methods for their manufacture
US4017648A (en) * 1975-02-03 1977-04-12 Xerox Corporation Toner agitation through microfield donor
US3996892A (en) * 1975-02-24 1976-12-14 Xerox Corporation Spatially programmable electrode-type roll for electrostatographic processors and the like
US5063412A (en) * 1990-09-26 1991-11-05 Xerox Corporation Development apparatus using an electromagnet to prevent development in the non-operative mode
US5289240A (en) * 1993-05-20 1994-02-22 Xerox Corporation Scavengeless developer unit with electroded donor roll
US5360940A (en) * 1993-07-14 1994-11-01 Xerox Corporation Scavengeless two component development with an electroded development roll
US5491538A (en) * 1994-07-05 1996-02-13 Xerox Corporation Development apparatus having an adjustable width development nip
EP0691586A1 (en) 1994-07-05 1996-01-10 Xerox Corporation Development apparatus having an adjustable width development nip
US5500969A (en) * 1994-10-24 1996-03-26 Xerox Corporation Dual polarity commutated roll elctrostatic cleaner with acoustic transfer assist
EP0709751A2 (en) 1994-10-24 1996-05-01 Xerox Corporation Apparatus for cleaning particles from a surface
US5614995A (en) * 1995-09-05 1997-03-25 Xerox Corporation Electroded donor roll having robust commutator contacts
US5570169A (en) * 1995-09-25 1996-10-29 Xerox Corporation Donor rolls with modular commutation
US5589917A (en) * 1995-09-25 1996-12-31 Xerox Corporation Donor rolls with magnetically coupled (Transformer) commutation
US5600418A (en) * 1995-09-25 1997-02-04 Xerox Corporation Donor rolls with exterior commutation
US5592271A (en) * 1996-01-11 1997-01-07 Xerox Corporation Donor rolls with capacitively cushioned commutation
US5594534A (en) * 1996-01-11 1997-01-14 Xerox Corporation Electroded doner roll structure incorporating resistive network
EP0785485A2 (en) 1996-01-11 1997-07-23 Xerox Corporation Electrodes donor roll structures incorporating resistive networks
EP0786707A2 (en) 1996-01-11 1997-07-30 Xerox Corporation Donor rolls with capacitively cushioned commutation
US5745827A (en) * 1997-03-31 1998-04-28 Xerox Corporation Bundled steel wire SED communicator secondary cores

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GB976998A (en) 1964-12-02
NL286833A (en)

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