US3823688A

US3823688A - Magnetic brush assembly

Info

Publication number: US3823688A
Application number: US00220965A
Authority: US
Inventors: S Klett
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1972-01-26
Filing date: 1972-01-26
Publication date: 1974-07-16
Anticipated expiration: 1991-07-16
Also published as: BR7300640D0; FR2169143A1; FR2169143B1

Abstract

A roller assembly for inclusion in a magnetic brush assembly wherein a floating bias is provided on a shaft of the roller assembly.

Description

United States Patent 1191 1111 3,823,688 K18 14 1 July 16, 1974 MAGNETIC BRUSH ASSEMBLY 3,219,014 11/1965 Mott et a1. 118/637 3,328,193 6/1967 O11 hant et a1. 117/37 [75] Inventor: Stanley Klett, 3,455,276 7/1969 Aniierson 118/637 3,574,301 4/1971 Bernhard. 118/637 [73] Asslgnee. corpomuon Stamford 3,575,139 4/1971 Nuzum 118/637 3,641,980 2/1972 Bickmore 118/637 [22] Filed: Jan. 26, 1972 3,654,893 4/1972 Piper et a1. 118/2 3,674,532 7/1972 Morse l17/17.5 1 1 pp 220,965 3,697,050 10/1972 Stanley 259/4 [52] US. Cl 118/637, 117/17.5, 118/623 Primary Examiner-Mervin Stein [51] Int. Cl G03g 13/00 sista mi r-L M ll-st in [58] Field of Search 118/623, 637; 117/l7.5

[57] ABSTRACT [56] References cued A roller assembly for inclusion in a magnetic brush as UNITED STATES PATENTS sembiy wherein a floating bias is provided on a shaft 2,902,974 Greaves of the oner assembly 3,040,704 6/1962 Bliss 118/637 3,152,924 10/1964 Wanielista et a1. 118/637 6 Claims, 6 Drawing Figures PATENTED JUL 1 SL974 I samzora PATENTEU JUL 1 81974 SIIEU30F3 1 MAGNETIC BRUSH ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to improvements in developing apparatus for electrostatic printing machines and more particularly to improvements in a roller assembly for a Pat. No. 2,297,691 to Chester F. Carlson, axerographic surface comprising a layerof photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the xerographic plate is electrostatically charged uniformly'over its surface and then exposed to a light pattern of theimage being reproduced to thereby discharge the charge in the areas where light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.

The latent electrostatic image may then be developed by contacting it with a finely divided electrostatically attractable material, such as a resinous powder. The powder is held in the image areas by the electrostatic fields on the layer. Where the field is greatest, the greatest amount of material is deposited; and where the field is last, little or no material is deposited. Thus, a powder image is produced in conformity with the light image of the copy beingreproduced; The powder is subsequently transferred to a sheet of paper orother surface and suitably affixed to thereby form a permanent print.

The electrostatically attractable developing material commonly used in magnetic brush developing appara tus comprises a pigmented resinous powder referred to here as tonerT and a"carrier of larger granular beads formed with steel cores coated with a material removed in the triboelectric series from the toner so that a triboelectric charge is generated between the toner powder and the granular carrier. The magnetizable carrier also provides mechanical control for the formation of brush bristles by virtue of magnetic fields so that the toner can be readily handled and broughtinto contact with the exposed xerographic surface. The toner is then attracted to the electrostatic latent image from the carrier bristles to produce a visible powder image on an insulating surface.

Generally, in an endless belt printing machine configuration which employs a plurality of magnetic brushes, the brushes are arranged for developing purposes with a run of the belt in the planar orientation.

ln copending application Ser. No. 97,856, filed Dec. 14, 1970, by Salvatore Latone and Michael R. Stanley, entitled Magnetic Brush Developing Apparatus," now U.S. Pat. No. 3,724,422, issuedApr 3, l97 3 M15155;

for reuse to the sump at the beginning end of the string by gravity forces. The brushes are mounted for rotation with conventional commutator brushes and rings which failed after relatively short periods of time.

OBJECTS OF THE INVENTION An object of this invention is to provide an improved roller assembly for a magnetic brush developing apparatus.

Another object of the invention is to provide an improved roller assembly for a magnetic brush developing apparatus for use in an electrostatic printing machine utilizing an endless belt photoreceptor.

Still another object of the invention is to provide an improved roller assembly for a magnetic brush developing apparatus which eliminates conventional commutator brushes and rings.

SUMMARYOF THE INVENTION These and other objects of the invention are obtained in a magnetic brush developing assembly by utilizing the bearings of the roller assembly as part of an electrical path for biasing the magnetic brushes.

DESCRIPTION OF THE DRAWINGS detailed disclosure thereof, especially when taken with the accompanying drawings, wherein like numerals designate like parts throughout.

FIG. 1 is a schematic sectional view of an electrostatic reproduction machineembodying the principles of the invention;

FIG. 2 is a top plane view of the roller assembly of the invention for a magnetic brush developer apparatusi FIG. 3 is a side view of the roller assembly of FIG. 2;

FIG. 4 is a partial sectional view of the roller positioned at the'beginning of the roller assembly;

FIG. 5 is a cross-sectional view of the roller of FIG. 4 taken along line 4--4.thereof; and

FIG. 6 is a partial sectional view of the other rollers of the magnetic brush developing assembly.

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. As in all electrostatic systems, such as a xerographic machine of the type illustrated, a light image of a document tobe reproduced is projected onto the sensitized surface of a xerographic plate to form an electrostatic latent image thereon. Thereafter, the latent image is developed with an oppositely charged developing material to form a xerographic powder image, corresponding to the latent image on the plate surface. The powder image is then electrostatically transferred to a support surface and fixed by a fusing device to cause the powder image to adhere permanently to the support surface.

In the illustrated machine, adocument D to be copied is placed upon a transparent support platen P 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.

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 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 if the arrow at a Constant rate. During exposure of the belt 12, the portion exposed is that portion of the belt running between rollers and 21. During such movement 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 A.

As the belt surface continues its movement, the electrostatic image passesthrough a developing station B in which there is positioned a developer assembly generally indicated by the reference numeral 15, and which provides development of the electrostatic image by means of multiple brushes 16 as the same moves through the development zone. The roller assembly of this invention is positioned within the developer assembly 15 to form a magnetic brush developing assembly.

The developed electrostatic image is transported by the belt to a transfer station C whereat a sheet of copy paper 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 developed 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 C.

Referring now to FIGS. 2 and 3 there is provided a roller assembly, generally indicated as 30, comprised of

end plates

32 and 34 which receive

rollers

36, 38, 40, 42 and 44 as more clearly hereinafter described. The

end plates

32 and 34 are provided with a plurality of holes 46 for mounting the roller assembly within the developer assembly 15 of the machine.

Referring to F IGS. 4 and 5, the roller 36 is comprised of a cylindrical sleeve 48 of a roughened surface formed of a non-magnetizable material and extending almost the length of the housing of the developing assembly, as illustrated in the aforementioned copending application of Latone et al. One end of the sleeve 48 is closed by a cap 50 which supports a drive shaft 52 in co-axial alignment with the sleeve 48. The other end of the sleeve 48 is closed by a cap 54 having an orifice 56 through which extends a shaft 58. Suitable bearing means 60 and 62 are provided on the shaft 58 which cooperates with inner bearing surfaces formed in the

end caps

50 and 54, respectively, to permit the sleeve 48 to rotate about shaft 58. Within the sleeve 48, there are positioned elongated bar magnets and 72 extending nearly the fully length of the sleeve 48 and suitably affixed to the shaft 58, such as by welding.

Referring now to FIG. 6, there is illustrated a roller 38 constituting one of the remaining rollers of the roller assembly 30, and is comprised of a cylindrical sleeve 82 of a roughened surface formed of non-magnetizable material and coextensive with sleeve 48 of the roller 36. One end of the sleeve 82 is closed by a cap 84 which supports a drive shaft 86. The other end of the sleeve 82 is closed by a cap 88 having an orifice 90 through'which extends a shaft 92. Suitable bearing means 94 and 96 are provided on the shaft 92 which cooperates with inner bearing surfaces fomed in

caps

84 and 88, respectively, to permit the sleeve 82 to rotate about the shaft 92. Within the sleeve 82, there is positioned an elongated bar magnet 98 extending nearly the full length of the sleeve 82 and suitably affixed to the shaft 92.

Referring again to FIGS. 1 and 2, the drive shaft of the

rollers

36, 38, 40, 42 and 44 are suitably mounted in bearings in end plate 32. The ends of the

drive shafts

52 and 86 of the roller 36 and

rollers

38, 40, 42 and 44 extending beyond the end plate 32 are provided with sprockets 102 and 104, respectively, suitably affixed to their respective drive shaft, such as by pins 106. The

shafts

58 and 92 of the roller 36 and

rollers

38, 40, 42 and 44, respectively, are keyed in end plate 34 by a flatened surface K formed on the ends of the shafts. A bias strap 108 is mounted to the ends ofthe shafts ofthe

rollers

36, 38, 40, 42 and 44, such as by screws 109 threaded into the screw receiving means formed in the ends of the shaft. The strap 108 is connected by a conductor 110 to a suitable current source to bias the roller assembly 30 in operation.

In operation, the

rollers

36, 38, 40, 42 and 44 are caused to rotate by a endless chain (not shown) engaging the sprockets affixed to the shafts of the respective rollers and driven by drive means (not shown) while the bar magnets in each roller remain stationary. The means for transporting developing means from the lower sump portion of the housing to the adjacent periphery of the cylinder 36 is described in the aforementioned copending application to Latone, et al.

During a development cycle when all cylinders are rotating in unison in the same direction with their respective magnetic bars held stationary, the brush bristles produced by the influence of the magnetic fleld emanating from the bar magnets acting upon the magnetizable carrier beads in the developing material will form on the surface of each sleeve between the sleeves and the surface of the photoconductor belt. Bristles remain formed during the developing cycle, being initiated by the influence of the pick-up device and maintained, during rotation of the sleeves. When the bristles move beyond the influence of the bar magnets of a sleeve beyond the closest distance between the belt and sleeve, bristle formation is maintained by the influence of the bar magnet of the next downstream sleeve. This phenomena is repeated until the last sleeve is reached whereupon the developing material is returned via the hereinabove mentioned chute assembly. A floating bias of a few microamps is supplied to conductor 110 from a suitable source (not shown).

While the description of the present invention has been directed to a magnetic brush apparatus having five rollers, it should be understood that less rollers, e.g., one roller, may be employed depending on the designed duty of the machine. Additionally,'while the invention has been described with reference to a machine having an endless photoconductive belt assembly, it is understood that the principle of the invention is applicable to a machine employing a photoconductor drum wherein one or more rollers are provided in the magnetic brush assembly.

While the instant invention as to its objects and advantages has been described herein as carried in specific embodiments thereof, it is not desired to be limited thereby; but it is intended to cover the invention broadly within the scope of the appended claims.

What is claimed is:

1. In a magnetic brush apparatus for applying developing material to a movable photoconductive surface including electrostatic latent images in an electrostatic printing machine, a brush roller assembly which comprises:

a rotatable sleeve member having first and second support shafts projecting from each end thereof, said first support shaft being secured to said sleeve member and rotatable therewith, said second support shaft being rotatable relative to said sleeve member and including a portion projecting within said sleeve member; magnet means within said sleeve .member on said second support shaft portion;

conductive bearing means between said sleeve member and said second support shaft to permit relative rotation therebetween;

a first end member adapted to rotatably support said first support shaft;

a second end member adapted to non-rotatably support said second support shaft, said first and second end members being mounted within said machine such that said sleeve member is disposed in operative juxtaposition to the photoconductive surface; and t conductor means electrically coupled to said sleeve member through said second sleeve supporting shaft and said bearing means whereby to supply bias directly to said sleeve without slip rings.

2. The apparatus as defined in claim 1 including plural roller assemblies, said conductor means being electrically connected to the second support shafts of each of said roller assemblies whereby to bias the sleeve members of each roller assembly.

3.'The apparatus as defined in claim 2 including means to rotate said first support shafts and the roller assembly sleeves secured thereto in the direction of movement of the photoconductive surface.

4. The apparatus as defined in claim 2 wherein said magnet means includes a pair of operating magnets for one of said roller assemblies, said magnet means for said other roller assemblies comprising one magnet.

5. The apparatus as defined in claim 4 wherein the diameter of the sleeve members of said one roller assembly is larger than the,diameter of the sleeve members of the remaining roller assemblies.

6. The apparatus as defined in claim 5 wherein the tangents to said roller assembly sleeves at the point closest to said photoconductive surface are located in aplane.

Claims

1. In a magnetic brush apparatus for applying developing material to a movable photoconductive surface including electrostatic latent images in an electrostatic printing machine, a brush roLler assembly which comprises: a rotatable sleeve member having first and second support shafts projecting from each end thereof, said first support shaft being secured to said sleeve member and rotatable therewith, said second support shaft being rotatable relative to said sleeve member and including a portion projecting within said sleeve member; magnet means within said sleeve member on said second support shaft portion; conductive bearing means between said sleeve member and said second support shaft to permit relative rotation therebetween; a first end member adapted to rotatably support said first support shaft; a second end member adapted to non-rotatably support said second support shaft, said first and second end members being mounted within said machine such that said sleeve member is disposed in operative juxtaposition to the photoconductive surface; and conductor means electrically coupled to said sleeve member through said second sleeve supporting shaft and said bearing means whereby to supply bias directly to said sleeve without slip rings.

3. The apparatus as defined in claim 2 including means to rotate said first support shafts and the roller assembly sleeves secured thereto in the direction of movement of the photoconductive surface.

5. The apparatus as defined in claim 4 wherein the diameter of the sleeve members of said one roller assembly is larger than the diameter of the sleeve members of the remaining roller assemblies.

6. The apparatus as defined in claim 5 wherein the tangents to said roller assembly sleeves at the point closest to said photoconductive surface are located in a plane.