US3866564A

US3866564A - Magnetic brush developing apparatus for copiers

Info

Publication number: US3866564A
Application number: US354416A
Authority: US
Inventors: Charles D Wilson
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-04-25
Filing date: 1973-04-25
Publication date: 1975-02-18
Anticipated expiration: 1992-02-18
Also published as: DE2415053A1; CA1016352A; JPS5028331A; GB1458317A

Abstract

An electrostatic type copier or reproduction machine having one or more magnetic brush devices for developing the latent electrostatic images formed on the copier photoconductive member, such magnetic brush devices ordinarily having a biasing voltage impressed thereon. To enable shorting of the magnetic brush or brushes to be detected, and, where desired, the shorted brush of a multiple brush system to be identified, a short responsive circuit is provided adapted when shorting is detected to actuate a predetermined control. The aforesaid control may comprise an operator signal lamp or a device to shutdown the copier.

Description

United States Patent [1 1 Wilson Feb. 18, 1975 1 MAGNETIC BRUSH DEVELOPING APPARATUS FOR COPIERS [75] Inventor: Charles D. Wilson, Fairport, NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: Apr. 25, 1973 21 Appl. No.: 354,416

[52] U.S. Cl 118/10, 1l7/17.5, 118/11, 118/637,118/4 [51] Int. Cl G03g 13/00 [58] Field of Search 118/7, 9, 10, 11,637; 117/175 [56] References Cited UNITED STATES PATENTS 2,902,974 9/1959 Greaves 118/637 3,219,014 11/1965 Mott et al. 118/637 3,638,614 2/1972 Young et al. 118/637 3.674.532 7/1972 Morse; 118/637 x 3,779,204 12/1973 Altmann 118/8 3,795,239

3/1974 Walberg", 317/3 Primary Examiner-Mervin Stein Assistant E.\'aminerLeo Millstein [57] ABSTRACT 7 Claims, 7 Drawing Figures FATENTED FEB18I875 SHEET 1 BF 4 FATENTEU FEB l 8|975 SHEET P. 0F 4 PATENTED FEB] 8l975 3.666564 sum nor 4 MAGNETIC BRUSH DEVELOPING APPARATUS FOR COPIERS This invention relates to a magnetic brush developing system for reproduction machines, and more particularly, to an improved magnetic brush developing system having means for detecting shorting of the system magnetic brush or brushes.

As will be understood by those familiar with electrostatic type reproduction and copier machines, the efficacy of such copiers depends in large measure upon the proper relative charge, i.e. the electrostatic development field, being maintained between the copier photoconductive member and the image developing materia. For, as appreciated, this electrostatic development field is relied upon to attract the ink portion of the developing material, i.e. the toner, to the photoconductive member in conformance with both the outline and density of the electrostatic latent image on the photoconductive member. It will be understood that the electrostatic image was previously formed through exposure of the charged photoconductive member to a light image of the original being copied.

Many copiers employ one or more magnetic brushes to bring the developing material into operative relationship with the photoconductive member. In effectuating this, the magnetic field generated by the brush or brushes serves initially to attract and hold the developing material on the periphery thereof and thereafter, due to the charge relationship between brush and photoconductive member, to release toner attracted to the photoconductive member in conformance with the latent electrostatic image. In this context, the developing material is composed of carrier particles or beads and toner, the toner particles, due to the triboelectric relationship between the carrier and toner materials, being normally attracted to the carrier. It is this carrier bearing toner that is brought by the developing mechanism, i.e. the aforesaid magnetic brushes, into juxtaposition with the photoconductive member to allow the electrostatic charges on the photoconductive member to draw the toner from the carrier beads and onto the photoconductive member in conformance with the latent electrostatic image thereon.

While the aforesaid carrier may comprise various materials and material compositions, in the case of magnetic developing systems, the carrier material must have magnetic properties in order for the magnetic brush or brushes to operate. However, this may give rise to a shorting problem since the magnetic carrier beads, which are normally a ferrite material, can, should they jam or conglomerate between a magnetic brush and the developing material housing, which is normally grounded, short the brush. This condition, which alters the operating bias on the magnetic brush or brushes affected, impairs or destroys developing efficacy.

It is a principal object of the present invention to provide a new and improved magnetic developing system for electrostatic type reproduction machines.

It is an object of the present invention to provide an electrostatic copier with magnetic brush type developer incorporating means to detect faulty operation of the magnetic brushes.

It is a further object of the present invention to provide a magnetic brush type developing apparatus for reproduction machines having means to signal the presence of ashort circuit in the magnetic brush developing apparatus.

It is an object of the present invention to provide an improved electrostatic copier having a multiple magnetic brush developer system incorporating means to identify a shorted brush.

It is another object of the present invention to provide an improved reproduction machine with magnetic brush developer having means responsive to a short in the developer to shut down the reproduction machine.

This invention relates to a reproduction machine for producing copies of originals, comprising, in combination, a photoconductive member adapted to be electrostatically charged to permit latent electrostatic images of an original being reproduced to be formed thereon during the reproduction process; developer means to bring developer material into operative relationship with the photoconductive member to develop the latent electrostatic image on the photoconductive member in preparation for transfer thereof to a supportmaterial, the developer means including at least one magnetic brush; means to provide a biasing voltage to the magnetic brush; and means adapted on shorting of the magnetic brush to generate a predetermined signal.

Other objects and advantages of the present invention will be apparent from the ensuing description and drawings in which:

FIG. 1 is a schematic sectional view of an electrostatic type reproduction machine incorporating the magnetic brush developing apparatus of the present invention;

FIG. 2 is a side view of the magnetic brush developing apparatus shown in FIG. 1;

FIG. 3 is an elevational view of the opposite side of the magnetic brush developing apparatus shown in FIG. 2 illustrating'the brush drives;

FIG. 4 is a top plan view of the magnetic brush developing apparatus showing details of the brush biasing means;

FIG. 5 is a first circuit embodiment illustrating the magnetic brush short detecting circuit of the present invention;

FIG. 6 is a second circuit embodiment illustrating a magnetic brush short detecting circuit effective to pinpoint the specific brush shorted; and

FIG. 7 is a third circuit embodiment illustrating a magnetic brush short detecting circuit adapted to shut down the reproduction machine in the event shorting of a magnetic brush occurs.

For a general understanding of the illustrated copier/reproduction machine in which the invention may be incorporated, reference is had to FIG. 1 in which the various system components for the machine are schematically illustrated.

A document 11 to be copied is placed upon a transparent support platen l6 fixedly arranged in an illumination assembly, generally indicated by the reference numeral 10, positioned at the left end of the machine. Light rays from an illumination system are flashed upon the document to produce image rays corresponding to the informational areas. The image rays are projected by means of an optical system onto the photosensitive surface of a xerographic plate in the form of a flexible photoconductive belt 12 arranged on a belt assembly, generally indicated by the reference numeral 14.

The belt 12 comprises a photoconductive layer of selenium which is the light receiving surface and imaging medium for the apparatus, on a conductive backing. The surface of the photoconductive belt is made photosensitive by a previous step of uniformly charging the same by means of a corona generating device or corotron 13. Power for corotron 13 is provided by a suitable power source.

The belt is journaled for continuous movement upon three rollers 20, 21 and 22 positioned with their axes in parallel. The photoconductive belt assembly 14 is slidably mounted upon two support shafts 23 and 24, with the roller 22 rotatably supported on the shaft 23 which is secured to the frame of the apparatus and is rotatably driven by a suitable motor and drive assembly (not shown) in the direction of the arrow at a constant rate. During exposure of the belt 12, the reflected light image of such original document positioned on the platen is flashed on the surface of the belt to produce an electrostatic latent image thereon at exposure station 27.

As the belt surface continues its movement, the electrostatic image passes through a developing station 28 in which there is positioned a magnetic brush developing apparatus, generally indicated by the reference numeral 30, and which provides development of the electrostatic image by means of multiple brushes as the same moves through the development zone, as more fully hereinafter described.

The developed electrostatic image is transported by the belt to a transfer station 29 whereat a sheet of copy paper or transfer member is moved between a transfer roller and the belt at a speed in synchronism with the moving belt in order to accomplish transfer of the devloped image solely by an electrical bias on the transfer roller. There is provided at this station a sheet transport mechanism, generally indicated at 17, adapted to transport sheets of paper from a paper handling mechanism, generally indicated by the reference numeral 18, to the developed image on the belt at the station 29.

. After the sheet is stripped from belt 12, it is conveyed into a fuser assembly, generally indicated by the refer ence numeral 19, wherein the developed and transferred xerographic powder image on the sheet material is permanently affixed thereto. After fusing, the finished copy is discharged from the apparatus at a suitable point for collection externally of the apparatus. The toner particles remaining as residue on the developed image, background particles and those particles otherwise not transferred are carried by the belt 12 to a cleaning apparatus 26 positioned on the rim of the belt between rollers and 22 adjacent a pre-clean corona generator 25. Further details regarding the structure of the belt assembly 14 and its relationship with the machine and support therefor may be found in the copending Application Serial No. 102,312, assigned to the same assignee.

Referring to FIGS. 2 through 4, there is illustrated a magnetic brush developing assembly, generally indicated as 30, comprising a series of rollers 36 rotatably supported in

frame end plates

32, 34. The rollers 36 are comprised of a cylindrical sleeve 46 of a roughened surface formed of a non-permeable material and extending almost the length of the housing of the developing apparatus 30. End sleeves 48, formed of an insulating material, are shrunk fit on each cylindrical sleeve 46 adjacent the ends thereof. One end of the sleeve 46 is closed by a cap 50 which supports a roller drive shaft 52 in coaxial alignment with the sleeve 46. The other end of the sleeve 46 is closed by a cap 54 having an orifice 56 through which extends shaft 58 of the internal bar magnets 61. Suitable bearing means 60 are provided to permit the sleeve 46 to rotate relative to shaft 58.

The roller drive shafts 52 are suitably mounted in bearings in end plate 32 and carry on their projecting ends drive sprockets 96. Sprockets 96 are formed of an insulating material.

Referring specifically to FIGS. 2 and 3, the magnet roller assembly 30 is disposed within a housing, generally indicated as 66, having a generally rectangular cross section and a length extending beyond the width of the photoconductive belt 12. Housing 66 is substantially closed except for an opening opposite photoconductive belt 12 whereat development of the latent image on belt 12 is effected. Housing 66 in effect serves as a container for developing material comprising carrier beads from magnetizable material and colored electrostatic toner particles which adhere thereto.

To provide bias potential to rollers 36, a suitable wiper 70 is provided in electrical contact with magnet shafts 58, wiper 70 extending along and being supported by side plate 34 to form an electrical path from a suitable power supply, shown schematically by battery 103, to each of the rollers 36. As will appear, in the FIG. 5 circuit embodiment the brush short detecting circuit is in series with the voltage line 71 while in the FIG. 6 circuit embodiment brush short detecting circuits are provided in the biasing circuits to individual magnetic brush rollers.

During development, the rollers 36 are rotated in unison in the same direction from a suitable drive source via sprockets 96, the internal bar magnets 61 remaining stationary. The brush bristles produced by the influence of the magnetic field emanating from the bar magnets 61 acting upon the magnetizable carrier beads in the developing material will form on the upper region of the sleeve 46 between the rollers 36 and the surface of the selenium belt 12.

This takes the form of a magnetic blanket" extending continuously over all of the brushes of rollers 36 for the entire width of the development zone 28 wherein the material is disposed or available to some degree for developing purposes. Further details regarding the formation and effect of the magnetic blanket" are described in the copending application Ser. No. 330,285, assigned to the same assignee.

Rollers 36 are biased to a predetermined voltage by battery 103, it being understood that the bias applied to magnetic brush rollers 36 cooperates with the electrostatic charge on belt 12 to establish an electrostatic development field in the developing area 28. The aforesaid electrostatic development field serves to attract toner particles to photoconductor belt 12 in conformance with the latent electrostatic image on belt 12. As will be understood by those skilled in the art, the aforesaid electrostatic development field is essential if the latent images on belt 12 are to be developed, and must be exactly controlled if optimum development of the latent image on belt 12 is to be attained. Accordingly, any uncontrolled change in the aforesaid electrostatic development field, such as occurs on shorting of one or more of the magnetic brush rollers 36, may degrade the image developed to a point where it is less than satisfactory.

The developing material normally comprises a carrier, usually small metal beads, and toner or ink particles. The carrier beads and toner are chosen for their triboelectric relationship.

The metal carrier beads may bear a coating of a suitable release material, and this type of bead, so long as the coating is perfect and remains intact and not worn off, is insulated. Other developing materials use uncoated metal beads. Should carrier beads of this type jam or compress together between a magnetic brush roller 36 and the housing 66, a current or ground path is formed, shorting the brush and changing the brush magnetic force. In addition, metal contaminants may be present in the developing material and this may short out one or more of the magnetic brush rollers 36.

Referring particularly to the circuit of FIG. 5, line 71 series connects magnetic brush rollers 36 with one another and with battery 103. A suitable indicator, which may comprise neon type lamp 110, is disposed in series with line 71. A suitable resistor 111 is provided in parallel with lamp 110. In this embodiment, a ground short in one or more of the magnetic brush rollers 36 increases the current flow through resistor 11] thereby generating sufficient voltage to cause lamp 110 to light. Preferably, lamp 110 is placed where it can be conveniently observed by the operator.

In the circuit embodiment of FIG. 6, a lamp 110' is series connected in the biasing circuit to each of the individual magnetic brush rollers 36. A resistor 111' parallels each lamp 110'.

On a short in one of the brush rollers 36, the lamp 110' associated therewith lights. By this arrangement, the operator is able to specifically identify the particular magnetic brush roller 36 shorted. Preferably, lamps 110 are disposed where they may be conveniently seen by the operator.

Instead of visually identifying or signalling the presence of a short in one of the magnetic brush rollers 36, or as an adjunct thereto, direct control may be exercised over operation of copier 10. In the schematic circuit representation of FIG. 7 a normally closed control switch 115 is provided in the control circuit 116 of copier 10. A suitable current sensitive switch relay 117 is arranged in series relationship with the bias line 71 to the magnetic brush rollers 36.

In the event of a short in any one of the magnetic brush rollers 36, the change in current through relay 117 energizes relay 117 to open switch 115 and actuate copier shutdown circuit 116. Circuit 116 stops copier l0, normally through a cycle out process. For this purpose suitable lock-out means (not shown) may be provided to inhibit restarting of copier 10 until the short condition has been corrected.

Other circuit arrangements for effectuating shutdown of the copier in the event of a short in one or more of the magnetic brush rollers 36 may be contemplated.

While the invention has been described with reference to the structure disclosed, it is not confined to the details set forth, but is intended to cover such modifications or changes as may come within the scope of the following claims.

What is claimed is:

1. In a reproduction machine for producing copies of originals having a photoconductive member on which latent electrostatic images of the original being reproduced are formed, with means for developing said latent electrostatic images in preparation for transfer thereof to support material, said developing means including at least one magnetic brush, together with biasing means to provide a biasing voltage on said magnetic brush, the improvement comprising:

signal indicator means;

energizing means for energizing said signal indicator means to produce a signal; and

brush short responsive means responsive to shorting of said magnetic brush to actuate said energizing means whereby to produce said signal.

2. The reproduction machine according to claim 1 in which said signal indicator means comprises a light.

3. The reproduction machine according to claim 1 in which said signal indicator means comprises means to shut down said reproduction machine on shorting of said magnetic brush.

4. The reproduction machine according to claim 1 in which said developing means includes at least two magnetic brushes, said signal indicator means comprising an indicator element for each of said brushes, said short responsive means responding to a short in one of said brushes to actuate said energizing means to energize the indicator element associated with said one brush.

5. As a control for visually indicating the presence of a short circuit in the magnetic brush developer section of an electrostatic type reproduction machine, said developer section having at least one magnetic develop ing brush, together with circuit means for imposing an operating bias on said brush, the combination comprising:

signal means in said circuit means in series relationship with said magnetic brush; and

means responsive to a predetermined change in current in said circuit means to actuate said signal means.

6. The control according to claim 5 in which said developer section includes plural magnetic brushes, said circuit means providing an individual bias circuit to each of said magnetic brushes, and

signal means in each of said magnetic brush circuits.

7. In a magnetic brush developing apparatus for reproduction machines, said developing apparatus including a housing within which developing material including bead-like particles of metallic carrier is provided, together with at least one roll-type magnetic brush disposed in operative relationship with said developing material, said magnetic brush being biased whereby to magnetically generate on the surface thereof a blanket-like covering of said developing material for use in developing latent electrostatic images, the combination of:

signal producing means;

energizing means for energizing said signal producing means to produce a signal; and

means responsive to grounding of said magnetic brush through said developing material carrier to actuate said energizing means whereby said signal producing means is energized and a signal reflecting grounding of said brush is produced.

Claims

1. In a reproduction machine for producing copies of originals having a photoconductive member on which latent electrostatic images of the original being reproduced are formed, with means for developing said latent electrostatic images in preparation for transfer thereof to support material, said developing means including at least one magnetic brush, together with biasing means to provide a biasing voltage on said magnetic brush, the improvement comprising: signal indicator means; energizing means for energizing said signal indicator means to produce a signal; and brush short responsive means responsive to shorting of said magnetic brush to actuate said energizing means whereby to produce said signal.

5. As a control for visually indicating the presence of a short circuit in the magnetic brush developer section of an electrostatic type reproduction machine, said developer section having at least one magnetic developing brush, together with circuit means for imposing an operating bias on said brush, the combination comprising: signal means in said circuit means in series relationship with said magnetic brush; and means responsive to a predetermined change in current in said circuit means to actuate said signal means.

6. The control according to claim 5 in which said developer section includes plural magnetic brushes, said circuit means providing an individual bias circuit to each of said magnetic brushes, and signal means in each of said magnetic brusH circuits.

7. In a magnetic brush developing apparatus for reproduction machines, said developing apparatus including a housing within which developing material including bead-like particles of metallic carrier is provided, together with at least one roll-type magnetic brush disposed in operative relationship with said developing material, said magnetic brush being biased whereby to magnetically generate on the surface thereof a blanket-like covering of said developing material for use in developing latent electrostatic images, the combination of: signal producing means; energizing means for energizing said signal producing means to produce a signal; and means responsive to grounding of said magnetic brush through said developing material carrier to actuate said energizing means whereby said signal producing means is energized and a signal reflecting grounding of said brush is produced.