US3916830A

US3916830A - Magnetic brush developer

Info

Publication number: US3916830A
Application number: US497523A
Authority: US
Inventors: Motoki Kojima; Nin-Ichi Kamogawa; Haruo Fujii
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 1971-05-26
Filing date: 1974-08-15
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04
Also published as: JPS482942U; JPS563720Y2; DE2225287B2; DE2225287A1; GB1376978A

Abstract

An improved scraping plate, in combination with a magnetic brush developer, is disclosed, which has an upwardly extending edge contacting the magnetic brush for removal of residual developer materials and a plurality of guide elements for moving the scraped residual developer materials axially whereby the developer materials are more uniformally mixed.

Description

i United States Patent Kojima et al. Nov. 4, 1975 MAGNETIC BRUSH DEVELOPER 1,201,971 10/1916 Kaiser 15/256.5l

3,233,586 2/1966 Cranskens et a1. 118/637 [75] Inventors Mmok' 3,319,563 5/1967 Champion @1111. 118/203 x Kamogawa, Tokyo; Haruo Fujii, Mltaka, all of Japan FOREIGN PATENTS OR APPLICATIONS [73] Assignee: Konishiroku Photo Industry Co. 110,249 4/1944 Sweden l5/256.51

Ltd., Tokyo, Japan [22] Filed: Aug. 15, 1974 Primary Examiner-Morris Kaplan [211 App] NO 497 523 Attorney, Agent, or Firm-Bierman & Bierman [30] Foreign Application Priority Data May 26, 1971 Japan ..46-42359 [57] ABSTRACT Related U.S. Application Data [63] 55:32: 2? of May 1972 An improved scraping plate, in combination with a magnetic brush developer, is disclosed, which has an [52] U S U 118/637, 118/203 upwardly extending edge contacting the magnetic [51] G03G 13/08 brush for removal of residual developer materials and [58] Fie'ld of 203 a plurality of guide elements for moving the scraped 15/2565 residual developer materials axially whereby the developer materials are more uniformally mixed. [56] References Cited UNITED STATES PATENTS 438,143 10/1890 Cornell 15/2565] 7 Chums 4 Drawmg Figures US. Patent N0v.4, 1975 Sheet1of2 3,916,830

US. Patent Nov. 4, 1975 Sheet2 0f2 3,916,830

MAGNETIC BRUSH DEVELOPER This application is a continuation of Ser. No. 256801, filed May 25, 1972, now abandoned, which claims the priority of Japanese application 42,359/1971 filed May 26, 1971.

This invention relates to a developing apparatus with a magnetic brush for use in visualization of an electrostatic latent image.

An electrostatic latent image can be formed in various methods. Commonly known is a method wherein photo image corresponding to an original is projected on a uniformly charged photo-conductive insulating layer and the charge on exposed portion is dissipated to form an electrostatic latent image. An alternative is the method wherein needle end discharge is effected imageweise on the insulating layer to form an electrostatic photographic latent image.

In order to visualize thus formed electrostatic latent image, a developer is used which comprises, for example, a magnetic carrier and a toner. In the practical operation, the developer is adhered to the peripheral surfaces of a cylindrical magnet assembly comprising a plurality of magnets arranged at the peripheral surface thereof with alternate polarity whereby the developer is kept in brush-shaped configuration. The developer kept in brush-shaped configuration is moved along the peripheral surfaces of the cylindrical magnet assembly and brought into contact with the electrostatic latent image so that the toner contained in the developer can be selectively adhered to the latent image thereby developing and visualizing the latter.

The above-mentioned developing method is generally referred to as magnetic developing process, for which a number of apparatus have been proposed. In one proposed embodiment, there is employed an apparatus wherein a developer is adhered directly on the peripheral surfaces of the cylindrical magnet assembly, which is rotated in turn so that the developer can be conveyed and brought into contact with the electrostatic latent image. In another proposed embodiment, there is employed an apparatus wherein a developer is adhered to the peripheral surface of a freely rotate cylindrical (non-magnetic) supporting member, which has magnets located inside thereof, and the developer is adhered to the peripheral surface of said cylindrical member, which is rotated in turn so that the developer can be conveyed and brought into contact with the electrostatic latent image. In still another embodiment, there is employed an apparatus in which a cylindrical (non-magnetic) supporting member has magnets located at the inner peripheral surface thereof, each of said magnets having a magnetic pole alternately different in polarity along the innerperipheral surface of said supporting member. In practical operation of this apparatus, a developer is conveyed in the direction opposite to the direction of rotation of the magnets and brought into contact with an electrostatic latent image by rotating the cylindrical magnets while the developer is selfrotated.

In these magneticbrush developing apparatus, there is employed a flat scraping plate which scrapes off the developer from the peripheral surface of a cylindrical magnet assembly or a cylindrical supporting member after the developer has passed a developing position at which it is brought into contact with an electrostatic latent image. This scraping operation is effected in order to keep the magnetic carrier-to-toner ratio constant throughout the operation so that the developed image having aneven and uniform density can be obtained at any time by the development.

The magnetic carrier-to-toner ratio of a developer will vary in response to the progress of development because the toner is consumed. In the conventional process, therefore, the developer having a varied magnetic carrier-to-toner ratio must be scraped off wholly or partly from the peripheral surface of the cylindrical magnet assembly comprising a plurality of magnets or the cylindrical supporting member having magnets located therein and then returned to a container accommodating a fresh developer, so as to adjust again the magnetic carrier-to-toner ratio at a constant level required for development. Thus, the developer conveyed to a developing position can be kept at a desired level of the magnetic carrier-to-toner ratio at any time.

However, the prior art flat scraping plate has an inherent disadvantage such that a large part of the developer will move in the direction of rotation of the magnetic brush and not in the axial direction of the latter within the container, because the plate allows the developer to drop only in the direction of the peripheral surface of the brush within the container after it has scraped off the developing formulation from the latter.

So far as the developer moves only in the direction of rotation of the magnetic brush, the portion having a low toner density is maintained without being improved if it is present in the developer. Consequently, the photo image visualized by means of such developing apparatus will have a streaky shade. Moreover, if the toner concentration of the developer becomes low, the magnetic carrier itself may adhere to the developing surface. Also, in the portion where the toner concentration is too high, the toner may adhere to the nonimage portion of the developing surface to produce fog.

The present invention has for its object to eliminate the above-mentioned disadvantage in the developing apparatus with a magnetic brush and provide an apparatus for developing an electrostatic latent image with a magnetic brush whereby toner concentration can be kept uniformly at any time so as to obtain a uniform developing effect.

It has been found that such apparatus for developing an electrostatic latent image with a magnetic brush can be obtained by providing close to the supporting surface of the brush a scraping plate which scrapes off from the peripheral surface of the brush a developer which has pressed through a developing position and displaces the thus scraped developer in the axial direction of rotation of the brush. It should be understood that the expression displacement of the scraped developer in the axial direction of rotation of the magnetic brush" means that said developer is allowed to move into any direction non-peripheral to the axis of rotation of the brush.

For better understanding of the invention, an embodiment thereof will be described below with reference to the accompanying drawings in which,

FIG. 1 is a longitudinal sectional view of one embodiment of the developing apparatus with a magnetic brush according to the invention,

FIG. 2 is an enlarged perspective view of the developer scraping plate of the apparatus shown in FIG. 1,

FIG. 3 is an enlarged perspective view of another embodiment of the developer scraping plate, and

FIG. 4 is a sectional view taken along line A A of FIG. 3.

In FIG. 1,

reference numerals

1, 2, 3, 4 and 5 denote a magnet respectively. The magnet l is located close to a developing position and serves to form a developer comprising a toner and an iron dust carrier into brushshaped configuration. Reference numeral 6 denotes a cylindrical supporting member which surrounds the magnets l, 2, 3, 4 and 5 and is rotated in the direction as shown by arrow A. Reference numeral 7 denotes a developing formulation comprising an iron dust carrier and a toner, which is supported in the periphery of the cylindrical supporting member 6 and is moved by rotation of the supporting member in the direction as shown by arrow A. Reference numeral 8 denotes a surface to be developed movable in the direction as shown by arrow B, 10 a container accomodating a developer and 11 an edge for putting the ear of the developing brush in order. Reference numeral 9 denotes a scraping plate which scrapes off the developer on the cylindrical supporting member 6 and has a shape as shown in FIG. 2. The scraping plate 9 is mounted close to the cylindrical supporting member 6. This plate comprises a base portion 21 which acts to scrape off the developer from the supporting member, inclined raised

portions

22, 22 which are spaced apart from one another at the rearward edge of the base portion and

inclined wing portions

23, 24 and 23, 24 which are integrally formed on both sides of each of the raised portions. In FIG. 2, there is shown only two sets each comprising a raised portion 22 and

wing portions

23 and 24. However, in practice, there are provided a large number of sets each including a raised portion and two wing portions. When the developer is scraped off from the cylindrical supporting member 6, it will slide on the base portion 21 in the direction as shown by arrow C. In the base portion 21 without raised portion 22, the developer will drop the rearward edge of the portion 21, whilst in the base portion 21 provided with a raised portion 22, the developer will slide along the portion 22 and drop through the

wing portions

23, 24 in the direction as shown by arrow D. Thus, the developer is moved by the raised portion 22 and the

wing portions

23, 24 also in the direction of rotary axis of the cylindrical supporting member 6. Therefore, even if there is a portion in which toner concentration is low in a developer, the portion is mixed with the developer present in other portions by the above-mentioned agitating effect of the scraping plate 9, thereby eliminating local difference in concentration and achieving uniform toner concentration.

FIG. 3 and FIG. 4 show another embodiment of the invention. A scraping plate 30 has a structure similar to that of the scraping plate 9 shown in FIG. 1 and FIG. 2 and includes a base portion 31, projecting parts 32 and

inclined wing portions

33, 34. Further, the

wing portions

33, 34 have

developer receiving portions

35, 36 secured at their respective forward ends. Below the scraping plate 30 is fixed rigidly an auxiliary plate 41, which has inclined

wing portions

37, 38. The

wing portions

33, 34 of the scraping plate 30 and the

wing portions

37, 38 of the auxiliary plate 41 are alternately located as shown in FIG. 3. The

wing portions

37, 38 have

developer receiving portions

39, 40 at their respective forward ends. The developer will drop partly between the wing portion 33 and the wing portion 34 adjacent thereto, and the remainder will drop between the wing portion 37 and the wing portion 38 adjacent thereto.

In this apparatus, the movement of the developer is more complicated than that in the apparatus as shown in FIG. 1, so that local uneveness in toner concentration can be quickly eliminated.

When the developer with a magnetic brush according to the present invention is used, the amount of the developer which is accommodated in the container may become uneven. However, in the bottom of the container 10 there is accommodated a developer enough to fill the space between the container and the cylindrical supporting member 6, so that there does not occur unevenness in the length of the ear of the developing brush due to unevenness in the amount of toner. This ensures, in combination with the fact the edge 11 is provided to put the ear of the brush in order, that unevenness in the amount of developer does not exert ill influence on developing effect.

While the invention has been described with reference to particular embodiments, it should be obvious that various changes and modifications are possible to those skilled in the art, so that it is intended that the invention be solely limited by the appended claims.

What we claim is:

1. In an apparatus for developing an electrostatic latent image, comprising a magnetic brush formed on a cylindrical member and disposed within a trough, a particulate developer comprising a magnetic carrier and a toner disposed in said trough, said cylindrical member partially immersed in said developer, means for rotating said cylinder, means for passing a latent image carrier in proximity to and in contact with the brush thereby developing said image, and scraping means for removing residual developer from said cylindrical member for return to said trough after development, said scraping means being located downstream of the zone of image development and extending along the longitudinal extent of said cylinder, the improvement which comprises said scraping means comprising a scraping plate extending upwardly and along said longitudinal extent and having a linear front edge in close proximity to said cylinder thereby adapted to remove the residual developer, said scraping means further comprising a plurality of transversely directed and oppositely inclined guide elements extending from the rear edge of said scraping plate for moving at least a part of the scraped residual developer axially of said cylinder whereby the magnetic carrier and toner particles removed from said cylinder are more uniformly mixed.

2. An apparatus according to claiml 1, wherein said guide elements are rearwardly extending from the rear edge of said scraping plate.

3. An apparatus according to claim 1, wherein said guide elements are placed under said scraping plate and rearwardly extending.

4. An apparatus according to claim 1, wherein said guide elements comprising two groups of the guide elements, a first group of the guide elements being spaced along said longitudinal extent of said cylinder and extending from the rear edge of said scraping plate, a second group of the guide elements being individually spaced under and between two adjacent guide elements of said first group and rearwardly extending from the rear edge of said scraping plate.

5. An apparatus according to cliarn 1, wherein said guide elements comprise a plurality of spaced panels rearwardly extending from the rear edge of said scraping plate and a panel element extending from each lateral edge of each said spaced panel and directed downwardly and outwardly with respect to said spaced panels and said scraping plate.

6. An apparatus for developing an electrostatic latent image comprising a rotatable magnetic brush formed on a cylindrical member and disposed within a trough, a particulate developer comprising a magnetic carrier and a toner disposed in said trough, said cylindrical member partially immersed in said developer means for passing a latent image carrier in proximity to and in contact with the magnetic brush thereby developing said image, a fixed scraping plate located downstream of the zone of image development extending along the longitudinal extent of said cylinder and having an upwardly extending front edge in close proximity to said cylinder thereby removing residual developer from the cylinder for return to said trough, said plate including a plurality of spaced panels extending rearwardly from the rear edge of said plate, and a panel element extending from each lateral edge of each said spaced panel and directed downwardly and outwardly with respect to said spaced panels and said scraper plate, whereby developer material removed from said cylinder is moved axially of said cylinder by each of said panel panel elements to more uniformly mix the carrier and toner particles.

7. An apparatus as in claim 6, wherein said spaced panels each extend upwardly with respect to said plate.

Claims

1. IN AN APPARATUS FOR DEVELOPING AN ELECTROSTATIC LATENT IMAGE, COMPRISING A MAGNETIC BRUSH FORMED ON A CYLINDRICAL MEMBER AND DISPOSED WITHIN A TROUGH, A PARTICULATE DEVELOPER COMPRISING A MAGNETIC CARRIER AND A TONER DISPOSED IN SAID TROUGH, SAID CYLINDRICAL MEMBER PARTIALLY IMMERSED IN SAID DEVELOPER, MEANS FOR ROTATING SAID CYLINDER, MEANS FOR PASSING A LATENT IMAGE IN PROXIMITY TO AND IN CONTACT WITH THE BRUSH THEREBY DEVELOPING SAID IMAGE, AND SCRAPING MEANS FOR REMOVING RESIDUAL DEVELOPER FROM SAID CYLINDRICAL MEMBER FOR RETURN TO SAID TROUGH AFTER DEVELOPMENT, SAID SCRAPING MEANS BEING LOCATED DOWNSTREAM OF THE ZONE OF IMAGE DEVELOPMENT AND EXTENDING ALONG THE LONGITUDINAL EXTENT OF SAID CYLINDER, THE IMPROVEMENT WHICH COMPRISES SAID SCRAPING MEANS COMPRISING A SCRAPING PLATE EXTENDING UPWARDLY AND ALONG SAID

5. An apparatus according to cliam 1, wherein said guide elements comprise a plurality of spaced panels rearwardly extending from the rear edge of said scraping plate and a panel element extending from each lateral edge of each said spaced panel and directed downwardly and outwardly with respect to said spaced panels and said scraping plate.