Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS3455276 A
Publication typeGrant
Publication dateJul 15, 1969
Filing dateMay 23, 1967
Priority dateMay 23, 1967
Also published asDE1752408A1
Publication numberUS 3455276 A, US 3455276A, US-A-3455276, US3455276 A, US3455276A
InventorsAnderson Glenn R
Original AssigneeMinnesota Mining & Mfg
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Magnetically responsive powder applicator
US 3455276 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

July 15, 1969 G. R. ANDERSON 3,455,276


United States Patent 3,455,276 MAGNETICALLY RESPONSIVE POWDER APPLICATOR Glenn R. Anderson, Minneapolis, Minn., assignor to Mmnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed May 23, 1967, Ser. No. 640,720

Int. Cl. Bb 5/02 U.S. Cl. 118-637 13 Claims ABSTRACT OF THE DISCLOSURE An applicator for magnetically responsive, finely divided particulate material comprising a magnetizable shaft, a number of elongate magnetic members disposed in an annular array about and extending along said shaft in close fitting relation with the radially inner and outer surfaces of adjacent members having opposite polarity, a non-magnetic sleeve disposed about the periphery of said array, and means affording relative rotation between said sleeve and said members.

This invention relates to an applicator for use in presenting magnetically responsive, finely divided particles against the surface of an article for application thereto.

The present invention is particularly useful in applying pigmented particulate material to an article to develop an image thereon. One example of such use is in develop ing imagewise a differentially conductive pattern formed by projecting a light image on a photoconductive web. The photoconductive web being positioned between an insulative layer, backed by an electrode, and a second electrode contacting the particulate or powder which is in electrically conductive contact between the second electrode and the photoconductive web.

Various patents have issued on devices for applying developers, but such devices have had limited success at applying an even deposition of the particulate material or developer powder on an image bearing member with a width of eight and one-half inches to thirteen inches.

Some of the previously known devices which include the use of polarized members or magnetic field-producing members are shown in U.S. Letters Patent Nos. 3,152,- 924 and 3,176,652. The first of these patented devices uses a plurality of angularly spaced magnets set in a nonmagnetic core with a plurality of short magnets aligned axially along the core in end-to-end relation to achieve a desired length for the device and with the magnets aligned so that corresponding poles on the radial edge of the magnets are facing or confronting one another. At each joint or area where the magnets butt together'the strength of field gradiant falls off; also, each magnet has a bit different strength. All of these factors result in an uneven buildup of powder on the surface of the sleeve.

To overcome this the patentees promote the idea of rotating the magnets and the non-magnetic outer sleeve in the same direction but at different speeds; thus the magnets shift their position with respect to the sleeve and tend to keep a uniform deposit of powder forming the brush on the sleeve. This applicator or brush is therefore considered to be unduly complicated and, when used with powders which comprise magnetic particles coated with pigmented resin or resins, the results are unsatisfactory.

The device described in the second patent, No. 3,176,- 652, particularly with reference to FIGURE 3 thereof, employs a fixed magnetic member which can be generally cylindrical in shape but which is formed with axially extending alternating flutes and ribs with each rib constituting a magnetic pole of a polarity opposite to that of the next adjacent rib. This spacing between poles of op- 3,455,276 Patented July 15, 1969 posite polarity, while providing a magnetic field which varies direction around the periphery, produces areas be tween the ribs having a reduced field. Consequently the amount of magnetic material held on the sleeve and the powder movement are decreased because the field varies with weak tangential magnetic field being present opposite the flutes. This deficiency was attempted to be cured by the use of a rough exterior surface on the sleeve. Also, since it is very difficult to forma strong magnetic member in this Way, magnetized with different adjacent poles, thisstructure is not satisfactory commercially or functionally. Both of these earlier devices thus fall short of having the capability of developing an image of uniform density.

The device of the present invention affords an applicator having a uniform field along its length and strong fields around its circumference.

The present invention provides an applicator for applying to a wide surface a dimensionally uniform deposition of magnetically responsive particulate material.

In practicing the present invention a plurality of magnetic members, which are formed preferably of oriented anisotropic permanent magnet material dispersed in a nonmagnetic immobilizing matrix, are disposed in a circular array about a core formed of a high magnetic permeability and low loss such as soft iron and a relatively rotatable non-magnetic sleeve which supports the particulate image-forming material to be moved from a hopper to engaging relation with an image carrying surface.

The novel features and advantages of the present invention will become more apparent to those skilled in the art after reading the following detailed description which refers to the accompanying drawing wherein:

FIGURE 1 is a vertical sectional view of an applicating roller formed in accordance with the present invention;

FIGURE 2 is a diagrammatic view showing the roller of the present invention in cross-section and its relation to other elements in a coating assembly;

FIGURE 3 is a perspective view illustrating one magnetic member;

FIGURE 4 is a graph showing the magnitude of the radial and tangential components of the circumferential magnetic field; and

FIGURE 5 is a netic field.

Referring now to the drawing, there is shown in FIG- URES 1 and 2 a developing assembly comprising an applying roll assembly 10 adjustably supported between suitable insulated side frame members 11 and 12. The assembly 10 comprises a core or shaft 13 formed of a material having a high magnetic permeability and low loss, e.g. soft iron, supported at opposite ends in the frame members. Positioned about the shaft 13 are an even number of magnetic members 14 and 15, which will be described in greater detail hereinafter. The members 14 graph showing the longitudinal magand 15 are positioned between a fixed washer 16 and a clamping washer 17. Rotatably mounted relative to the shaft 13, as by bearing mounted end caps 18 and 19, is a non-magnetic cylindrical sleeve 20 formed of a material which will not shield the magnetic field from members 14 and 15. On each end of sleeve 20 is a drive ring 21 against which and in driving contact therewith are drive discs 22 supported by a driven shaft 23. Shaft 23 is journalled and adjustably mounted in the frame members 11 and 12 and has a drive pulley 24 on one extended end thereof which may be suitably driven from a belt 25 from a motor (not shown).

As desired in some copying applications, the applicating roll should serve as an electrode; therefore it is desired to connect the sleeve 20 to a source of electrical potential; and in the illustrated embodiment a connector 26 is attached to the shaft 13, to which a lead from a source of potential may be coupled. The sleeve 20 is electrically connected to the shaft 13 by a sliding leaf 27 of U-shaped resilient conductive material. The sleeve in this example is preferably formed of aluminum but could be formed of another non-magnetic material such as glass with an electrically conductive, non-magnetic surface coating.

The roll assembly 10, in operation, is positioned above a tray 30, mounted between the side frame members 11 and 12 and positioned for parallel aligned spaced relation to a rotating drum surface as illustrated at 31 or to a linear or convexly supported moving belt or web. In any instance if the relatively moving surface 31 is to be coated it carries an undeveloped image pattern to which is to be applied an even coating of particulate image-forming magnetically responsive material hereinafter referred to'as powder 33, which may be supplied to the roll assembly from a supply disposed in the hopper-like tray 30.

The tray 30 has an adjustable doctor blade 34 mounted along a forward upturned lip which permits spatial adjustment relative to the outer surface of sleeve 20. In operation, depending on how compressed or how much powder is desirable at the nip area between the sleeve 20 and surface 31, the doctor blade 34 may be adjusted between 0.010 inch and 0.05 inch. The position of the sleeve 20 is also adjustable toward and away from the surface 31 to afford light contact between the powder 33 and the surface 31 or some compressive pressure on the powder at the interface between the sleeve and the surface. Suitable means, such as slots in frame members 11 and 12 and pivoted mounting brackets, may be provided as illustrated in the drawing to permit movement of the shafts 13 and 23 relative to the surface to be coated; and suitable means, such as a screw adjusted lever arm keyed to shaft 13, permits rotatable adjustment of shaft 13. This adjustment of shaft 13 allows accurate positioning of either a radical edge to be normal to the surface to be coated or permits the rotation of shaft 13 to position the center of a magnetic member 14 or 15 nearest the surface to be coated.

The magnetic members 14 and 15 are alternately magnetically polarized elongate members which are generally shaped as sectors of a ring or sectors of a hollow cylinder having radially inner faces 35 concavely curved and convex radially outer surfaces 36 joined by radially extending edge walls 37. The shape of the members result in some vagaries in the dimensions and, although the members generally contact each other, a slight gap may exist in the array between one or more members and not disturb the performance. The members 15 are polarized to have a different magnetic pole on the outer surface than on the inner face; for example, the north pole indicated at N is on the outer surface 36, and the south pole indicated at S is along the inner face 35, The members 14 would be oppositely polarized with N on the inner face and S along the outer surface.

The members 14 and 15 are formed by extrusion of a non-magnetic matrix which may be a resinous or plastic composition, an elastomeric semi-solid, or viscous liquid, capable of hardening, setting or being cured to a solid state in which is evenly dispersed anisotropic ferrite domain-sized particles, which particles are capable of achieving physical orientation when acted upon by internal shear stresses. Examples of the particles are certain fine grain permanent magnet materials particularly the ferrites of barium, lead and strontium which are easily magnetized to saturation. The matrix may be natural rubber with compound agents, plasticizers, vulcanizing agents, and the like to provide the hardness of the matrix desired, or may be a thermoplastic or thermo-setting material, as for example polyvinyl chloride. Preferably the ferrite particles are oriented such that each particle (as illustrated diagrammatically in FIGURE 3 at 40) is positioned with its magnetic poles positioned radially relative to each other.

An even number of the wedge-shaped members 14 and 15 are alternately placed in a circular array about each member and extends axially along the shaft 13 for the length of application desired. The members 14 and 15 provide, with a 1 to 1 ratio between the radial dimension and the circumferential dimension, a surprisingly high flux density and, in the preferred annular array, provide a circumferential field with strong radial and tangential components. In FIGURE 4 the fiux density about the array of magnetic members 14 and 15 is plotted in gauss with the radial field component plotted in solid lines and the tangential field component plotted in dotted lines. The maximum radial field exists along a radial line bisecting the magnetic members, and the plot illustrates a flux density at the poles of 500 gauss. An optimum design is between 500 and 750 gauss at the poles. The tangential flux density peaks between the magnetic members and is illustrated on the plot at 300 gauss.

FIGURE 5 shows a graph along the length of the magnetic members and illustrates the readings above one pole as it is scanned from end to end. This graph'illustrates the uniformity of the magnetic fi'eld along the entire length of the magnetic members and that the field falls only at the ends. This uniformity of field affords a very uniform powder application by a roll assembly constructed in accordance with this invention.

In operation, rotation of the sleeve 20, which sleeve has a smooth outer surface with a diameter of approximately 1.250 inches and inside diameter of 1.180 inches, with a minimum clearance about the surface of the magnetic members of about .005 inch, carries the developing powder 33 from the tray 30 across the doctor blade 34. The powder particles appear to tumble under the effects of the changing directions of the magnetic field and move in the direction of rotation of the sleeve 20. The powder appears as a dark stripe on the areas of the sleeve above the poles and gray above the joint between the magnetic members. As the orientation of the ferromagnetic particles achieve a more exacting radial orientation in the matrix, the gray stripe is reduced to a line. The tumbling powder stands on the sleeve surface as tree rows and, when carried by clockwise rotation of sleeve 20 toward the clockwise rotating or oppositely moving surface 31, they will contact the surface to be deposited in the desired manner.

The spacing between sleeve 20 and surface 31 relative to the spacing between doctor blade 34 and the sleeve will determine the amount of powder per unit area placed in contact with the surface 31. The uniform axial field along the sleeve provides for uniform coverage across the surface 31 to be coated. In most applications the surface to be coated has a width of from 8 /2 to 14 inches, or the width or length of copy sheets.

Magnetic members formed of metallic alloys such as for example the materials sold under the trade name Alnico cannot be produced with a uniform field in lengths greater than 3 to 6" because, during the heat treatment, they warp and are unusable in this type of application. The short segments require them to be cemented together; and at each joint the uniformity of the field along the axis of the roller is disrupted because the field falls off sharply at the ends of the segments and the segments are not identical. The uniformity achieved by a developing roll assembly formed in accordance with the present invention appreciably reduces the variations in powder buildup on the roller or variations in density on the developed image.

Having thus described the present invention with reference to one embodiment, it is realized that one skilled in the art may make certain modifications without departing from the spirit and scope of this invention as defined in the pending claims.

What is claimed is:

1. An applicating roller for placing a uniform layer of magnetically responsive dry particulate material in contact with a surface moved past the peripheral surface of said roller, said applicating roller comprising a shaft of high magnetic permeability material, a plurality of elongate, generally sector-shaped in cross section magnetic members formed of fine grain permanent magnet material dispersed in a non-magnetic immobilizing matrix, which members are positioned With the edges thereof generally radial and in side-by-side relation to define a circular array around said shaft, and the radially inner and radially outer faces of each member being arcuate with said radially inner and radially outer faces of adjacent members in said array being oppositely polarized, a uniform non-magnetic hollow cylindrical sleeve positioned over said array of magnetic members and extending axially relative .to said shaft, and means for mounting said sleeve and said shaft for relative rotation to carry a quantity of said particulate material on the outer surface of said sleeve;

2. An applicating roller as claimed in claim 1 wherein said dispersed material in the magnetic members is oriented antisotropic substantially domain size particles of a permanent magnet material.

3. An applicating roller as claimed in claim 1 wherein said dispersed material consists of substantially domain size particles of material selected from the class consisting of the ferrites of barium, strontium and lead.

4. An applicating roller as claimed in claim 1 wherein eight magnetic members form a circular array about the shaft.

5. An applicating roller as claimed in claim 1 wherein said sleeve is electrically conductive.

6. An applicating roller as claimed in claim 1 wherein each of said magnetic members has an axial length of between 8 and 14".

7. A powder applicator comprising in combination:

(a) an applicating roller for applying magnetically responsive dry pigmented material onto a surface moved past the periphery of said roller, said applicating roller comprising a shaft formed of high magnetic permeability and low loss material; a plurality of elongate generally truncated sector-shaped magnetic members formed of ferrite permanent mag" net substantially domain sized particles oriented in a non-magnetic matrix, which members are arranged in side-by-side contacting relation and form a circular array about said shaft with radially outer surfaces of adjacent magnetic members having opposite polarity; a thin-Walled hollow cylindrical sleeve formed of non-magnetizable material positioned about and approximate to said array of magnetic members; and means for mounting said sleeve and said shaft for relative rotation, each of said magnetic members extending along a substantial portion of said shaft and covered by said cylinder;

(b) a tray for storing a supply of a said developer material in which said sleeve may come in contact; and

(c) means for rotating said sleeve and said shaft relative to each other to carry developer material from said tray about the surface of the sleeve into contact with surface to be developed.

8. A powder applicator as claimed in claim 7 wherein said shaft and magnet members are fixed and said sleeve is rotated about said shaft.

9. A powder applicator as claimed in claim 7 wherein said sleeve has an electrically conductive outer surface and is connected to a source of electrical potential,

10. A powder applicator as claimed in claim 8 wherein said sleeve has an electrically conductive outer surface and is connected to a source of electrical potential.

11. A powder applicator as claimed in claim 10 wherein means are provided for adjusting the position of said shaft.

12. An applicator for developing an image on a surface with a pigmented finely divided dry magnetically responsive developer material comprising in combination,

a tray adapted to receive sai-d developer material,

an applicating roller positioned relative to said tray for moving said developer material out of said tray, said applicating roller comprising a shaft of high magnetic permeability material,

a plurality of elongate, generally sector-shaped in cross section, magnetic members which are formed of oriented fine grain permanent magnet material dispersed in a non-magnetic immobilizing matrix and which have longitudinal edges which are generally radial and positioned with said edges in side-by-side contacting relation to form an arcuate array on the outer circular periphery of said shaft, said members also having arcuate radially inner and radially outer faces with said radially inner and radially outer faces of adjacent members in said array being oppositely polarized, and

a uniform non-magnetic hollow cylindrical sleeve positioned over said array and mounted for rotation relative to said shaft and said magnetic members and rotatable relative to said tray,

a doctor blade adjustably mounted on an edge of said tray adjacent the periphery of said sleeve for limiting the amount of said developer material which may be carried by said sleeve out of said tray upon rotation of said sleeve, and

means for rotating said sleeve.

13. An applicator as defined in claim 12 wherein a tangential magnetic field is formed between each of said adjacent magnetic members directly above said contacting edges where the field gradient is large, which field on the surface of said sleeve has a value of at least about 300 gauss.

References Cited UNITED STATES PATENTS 3,040,704 6/ 1962 Bliss 118-637 3,191,106 6/1965 Baermann 335-303 X 3,219,014 11/1965 Mott et al. 118-637 FOREIGN PATENTS 1,417,724 10/1965 France.

1,071,697 6/ 1967 Great Britain.

PETER FELDMAN, Primary Examiner US. Cl. X.R.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3040704 *Apr 16, 1957Jun 26, 1962Rca CorpApparatus for developing electrostatic printing
US3191106 *Oct 6, 1960Jun 22, 1965Baermann MaxRubber-like permanent magnet article and manufacture of same
US3219014 *Dec 4, 1962Nov 23, 1965Xerox CorpMechanical shield to protect magnetic core in xerographic developing apparatus
FR1417724A * Title not available
GB1071697A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3584601 *Oct 28, 1968Jun 15, 1971Xerox CorpMagnetic brush belt development
US3641980 *Oct 20, 1969Feb 15, 1972Xerox CorpDevelopment apparatus
US3643629 *Oct 20, 1969Feb 22, 1972Minnesota Mining & MfgMagnetic powder applicator
US3823688 *Jan 26, 1972Jul 16, 1974Xerox CorpMagnetic brush assembly
US3828730 *May 16, 1972Aug 13, 1974Hitachi Metals LtdElectrostatic record developing apparatus
US3863603 *Jan 7, 1974Feb 4, 1975IbmMagnetic brush roll having resilient polymeric surface
US3882821 *Mar 12, 1973May 13, 1975Canon KkDeveloping device for electrophotography
US3892908 *Jun 25, 1973Jul 1, 1975Minnesota Mining & MfgCoating of solid substrates with magnetically propelled particles
US3911865 *Mar 30, 1973Oct 14, 1975Xerox CorpToner pickoff apparatus
US3937181 *May 22, 1974Feb 10, 1976Fuji Xerox Co., Ltd.Magnetic brush type developing mechanism in electrophotographic copying machine
US3950089 *Feb 24, 1975Apr 13, 1976Xerox CorporationCoated roll for magnetic brush development and cleaning systems
US3952701 *Nov 5, 1974Apr 27, 1976Hitachi Metals, Ltd.Electrostatic developing apparatus
US3968773 *Mar 3, 1975Jul 13, 1976Xerox CorporationMagnetic brush developing apparatus
US3981271 *Feb 18, 1975Sep 21, 1976Fuji Xerox Co., Ltd.Magnetic brush type developer for use in an electrophotographic machine
US4040387 *Apr 22, 1975Aug 9, 1977Mita Industrial Co. Ltd.Electrostatic photographic copying apparatus
US4068622 *Oct 18, 1976Jan 17, 1978Oce-Van Der Grinten N.V.Magnetic roller
US4089297 *Oct 1, 1976May 16, 1978Konishiroku Photo Industry Co., Ltd.Developing apparatus of magnetic brush type for electrophotographic reproduction
US4102305 *Jul 1, 1977Jul 25, 1978Xerox CorporationDevelopment system with electrical field generating means
US4149488 *Nov 21, 1977Apr 17, 1979Siemens AktiengesellschaftDeflecting guide for developer mixture
US4166263 *Oct 3, 1977Aug 28, 1979Hitachi Metals, Ltd.Magnetic core assembly for magnetizing columnar permanent magnet for use in electrostatic developing apparatus
US4167718 *Oct 3, 1977Sep 11, 1979Hitachi Metals, Ltd.Dies set for magnetizing outer surface of magnetic column
US4168481 *Oct 5, 1977Sep 18, 1979Hitachi Metals, Ltd.Core assembly for magnetizing columnar permanent magnet for use in an electrostatic developing apparatus
US4169998 *Oct 3, 1977Oct 2, 1979Hitachi Metals, Ltd.Iron core assembly for magnetizing columnar permanent magnets for use in electrostatic developing apparatus
US4266328 *May 10, 1979May 12, 1981Hitachi Metals, Ltd.Developing roll for use in electrostatic developing apparatus employing magnetic particles
US4266868 *Jul 16, 1979May 12, 1981Minnesota Mining And Manufacturing CompanyMultiple roll developing apparatus
US4267245 *Jul 11, 1980May 12, 1981Minolta Camera Kabushiki KaishaMethod of removing foreign materials from magnetic developers
US4267248 *Feb 26, 1979May 12, 1981Hitachi Metals, Ltd.Magnet-brush development process of electric pattern images
US4277552 *Dec 3, 1979Jul 7, 1981Hitachi Metals, Ltd.Magnetic developing process and toner containing high coercive force magnetic powder
US4389478 *Jun 22, 1981Jun 21, 1983Bell & Howell CompanyApparatus for and methods of making bimodal electrophotographic copies
US4453492 *Aug 12, 1982Jun 12, 1984E. I. Du Pont De Nemours And CompanyMagnetic developing unit with improved toner decorator for magnetic printing
US4454520 *Jun 24, 1982Jun 12, 1984Honeywell Inc.Electrographic recorder with enhanced writing speed
US4496232 *Jun 8, 1981Jan 29, 1985Bell & HowellApparatus for and methods of making bimodal electrophotographic copies
US4834871 *Oct 28, 1987May 30, 1989Khd Humboldt Wedag AgMagnet block arrangement having an outwardly-directed field
US4839690 *May 26, 1988Jun 13, 1989Canon Kabushiki KaishaImage bearing member usable with image forming apparatus
US5494172 *May 12, 1994Feb 27, 1996Miller Compressing CompanyMagnetic pulley assembly
DE2224624A1 *May 19, 1972Nov 30, 1972Hitachi Metals LtdTitle not available
DE2523811A1 *May 27, 1975Dec 18, 1975Minnesota Mining & MfgVerfahren und einrichtung zum auftragen eines farbpulvers auf ein elektrographisches aufzeichungsmittel
DE2832695A1 *Jul 26, 1978Feb 8, 1979Tokyo Aircraft Instr CoMaschine zur bildentwicklung
DE4012698A1 *Apr 20, 1990Oct 25, 1990Minolta Camera KkMagnetische rolle zur verwendung in einem entwicklungsgehaeuse
EP0024110A1 *Jul 4, 1980Feb 25, 1981Minnesota Mining And Manufacturing CompanyMultiple roll developing apparatus
EP0027729A2 *Oct 17, 1980Apr 29, 1981Xerox CorporationApparatus for developing an electrostatic latent image
EP0027729A3 *Oct 17, 1980May 20, 1981Xerox CorporationApparatus for developing an electrostatic latent image
U.S. Classification399/126, 209/219, 335/303, 399/274
International ClassificationG03G15/09, G03G9/083
Cooperative ClassificationG03G15/0921, G03G9/083
European ClassificationG03G9/083, G03G15/09E