US3882823A - Stirring and scraping device for developing material - Google Patents

Abstract

A stirring and scraping device for developing material for use in an electrophotographic copying apparatus which comprises a rotary member rotatably provided below a toner dispenser and adjacent to a rotary developing roller in which stationary magnets are enclosed. The rotary member further includes a rotary shaft provided with many equally spaced grooves cut around the shaft so as to form a roller portion having many square edges. Upon rotation of the member in engagement with the developing roller the developing material on the developing roller is attracted by the member magnetized by the stationary magnets and subsequently detached from the member by centrifugal force and its own weight while being sufficiently stirred and mixed with fresh toner powder from the toner dispenser.

Description

United States Patent Tanaka et a1.

STIRRING AND SCRAPING DEVICE FOR DEVELOPING MATERIAL Inventors: Susumu Tanaka, Sakai; Yuji Enoguchi, Osaka; Hidetoshi Kawabata, Tondabayashi, all of Japan Minolta Camera Kabushiki Kaisha, Osaka, Japan Filed: July 9, 1974 App]. No.: 486,839

Assignee:

Foreign Application Priority Data Aug. 2. 1973 Japan 48-91615 U.S. c1. 118/637; 117/175; 118/70; 118/104; 118/203; 355/15 1111.0 G03g 13/08 Field 61 Search 118/70, 203, 262, 637, 118/623, 104; 355/3 DD, 15; 117/175 References Cited UNITED STATES PATENTS 3,608,522 9/1971 Davidson 118/637 3,648,656 3/1972 Ogawa 117/175 3659311 5/1972 Waren 355/15 Primary E.\'an11'ner-Mervin Stein Assistant E.\'aminerDouglas Salser Attorney. Agent, or Firn1Wenderoth, Lind & Ponack [57] ABSTRACT A stirring and scraping device for developing material for use in an electrophotographic copying apparatus which comprises a rotary member rotatably provided below a toner dispenser and adjacent to a rotary developing roller in which stationary magnets are enclosed. The rotary member further includes a rotary shaft provided with many equally spaced grooves cut around the shaft so as to form a roller portion having many square edges. Upon rotation of the member in engagement with the developing roller the developing material on the developing roller is attracted by the member magnetized by the stationary magnets and subsequently detached from the member by centrifugal force and its own weight while being sufficiently stirred and mixed with fresh toner powder from the toner dispenser.

13 Claims, 6 Drawing Figures PATENTEI] HAY l 3l975 SHEET 1!)? 2 FIG. I

FIG. 2

PATENTED HAY I 31975 SHEET 2 BF 2 c IIIOII HIGH 2 8 STIRRING AND SCRAPING DEVICE FOR DEVELOPING MATERIAL The invention relates to a dry-copying process electrophotographic copying apparatus, and more particularly to a stirring and scraping device for developing material for use therein.

Commonly, in a dry-copying process electropliotographic copying of xerographic or similar systems, subsequent to projection of light image of an original to be copied onto a charged photoreceptor surface to form an electrostatic latent image thereon, the latent image is developed at a developing station by rubbing the latent image formed portion with magnetic brush bristles of developing material comprising magnetizable carrier material and electoscopic toner powder to produce an electroscopic toner powder image in the configuration of the latent image on the photoreceptor surface for transfer onto a copy paper sheet so as to obtain a copy of the original image thereon.

In the above developing, it is absolutely necessary to use the developing material in which the toner particles are uniformly charged by the carrier material by thoroughly stirring and mixing the toner particles and carrier material in order to obtain an optimum toner powder image without any blur. If the latent image is developed by the developing material with insufficiently charged toner particles by the carrier material, it is difficult to obtain a good toner powder image due to the blur caused by toner particles spreading as far as nonimage formed portion on the photoreceptor surface, which trend results from weak electrostatic attraction between the carrier material and the toner particles or complete absence of such attraction therebetween.

Conventionally, stirring of the developer material is carried out by rotating stirring vanes of non-magnetic material partially or totally buried in the developer material which is accommodated in the developer housing in order to achieve uniform frictional charging between the carrier material and toner particles, which method, however, has such disadvantages that a large space is required at the bottom portion of the developer housing so as to accommodate the stirring vanes and to always store sufficient quantity ofdeveloper material required for stirring, and that stirring efficiency is remarkably reduced by the difficulty for stirring when the developer material in the developer housing is decreased to a certain level.

It is another disadvantage with such conventional devices that the developing material is fatigued or deteriorated due to the heat generated therein when subjected to strong compression and friction as the stirring vanes rotate.

Furthermore. according to the conventional devices of the above described type. the used developing material remaining on the outer periphery of the developing roller is scraped. after completion of the development, off the developing roller as the latter rotates, by a scraping plate of non-magnetic material disposed adjacent to the developing roller, in which practice, however, heat is generated by the friction between the developing material and the scraping plate, and the heat thus produces together with the heat arising from the adoption of the stirring vanes increases the fatigue of the developing material.

Accordingly, an essential object of the present invention is to provide a stirring and scraping device for developing material which will maintain uniform copying quality without generating any heat in stirring and scraping with substantial elimination of the disadvantages inherent in the conventional stirring and scraping devices.

Another important object of the present invention is to provide a stirring and scraping device of the above described type which is simple in construction and easy ofmaintenance with efficient stirring performance. and can be manufactured at low cost.

A still further object of the present invention is to provide a stirring and scraping device of the above described type which is compact in size and contributes much to smaller size of the copying apparatus.

According to a preferred embodiment of the present invention, a stirring and scraping member of a magnetic material in the form of a roller is rotatably provided below a toner dispensing device and adjacent to the surface of a rotary developing roller in which three bar magnets are fixedly disposed at an angle of approximately 90 to one another with one of the magnets facing the stirring and scraping member and another magnet directed to a photoreceptor surface. The member comprises a shaft rotatably journaled in the side walls of a developer housing with a pair of friction rollers secured to the shaft adjacent the opposite ends thereof which engage the surface of the developing roller for synchronous rotation with the latter. Many equally spaced concave grooves are cut around the shaft between the friction rollers to form a roller portion with many square edges on the shaft between the friction rollers, so that developing material remaining on the developing roller is positively attracted to the member magnetized by the stationary magnet during rotation of the member and the developing roller, and then detached from the member by the decreasing magnetic force and the centrifugal force arising from the rotation thereof and also by the own weight of the developing material while being fully stirred and mixed with fresh toner powder replenished from the toner dispenser as the member rotates.

As is seen from the above, according to the stirring and scraping device of the present invention, the developing material is perfectly stirred and mixed with toner powder for imparting sufficient frictional charge to the toner particles without developing any heat during stirring and scraping, and consequently without fatigue or deterioration of the developing material, resulting in uniform copying quality.

These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred em bodiment thereof with reference to the accompanying drawings, in which:

FIG. 1 is a schematic cross sectional view ofa stirring and scraping device of the invention and mechanisms of a developing device associated therewith,

FIG. 2 is a perspective view of the device in FIG. 1 with a toner dispener and photoreceptor drum removed,

FlG. 3 is a schematic cross sectional view ofa modification of the stirring and scraping device with associated mechanisms of a developing device of FIG. 1,

FIG. 4 is a rear elevational view, partly in section, of the device of HO. 3,

FIG. 5 is a perspective view of a modification of the stirring and scraping device in FIG. I, and

FIG. 6 is a perspective view of another modification of the stirring and scraping device in FIG. 1.

Before the description of the present invention proceeds, it is to be noted that like parts are designated by like numerals throughout the several views of the accompanying drawings.

Referring to FIGS. 1 and 2, there is shown a known photoreceptor drum 3 having a photoreceptor surface 3a on the outer periphery thereof rotated in the direction of an arrow A by a conventional means. A developing device A extending the width of the photoreceptor surface 3a is substantially enclosed in a housing 2 except for an opening Al adjacent to the photoreceptor surface 3a whereat development of an electrostatic latent image formed on the surface 3a is effected and an opening A2 in which a toner tank 14 for a toner powder dispenser 13 is releasably received to replenish the toner powder depleted from a developing material 12 during development of the electrostatic latent image. At the lowermost portion of the housing 2, there is provided a sump 20 containing the developing material 12 comprising magnetizable carrier material and electroscopic toner particles. A rotary developing roller 1 provided at a lower portion of the housing 2 adjacent to the photoreceptor surface 3a through the opening Al comprises an outer cylinder la of a nonmagnetic material extending the width of the housing 2 and rotatably journaled in the side walls 2a and 2b of the housing 2 so as to be rotated by a suitable driving means (not shown) with stationary elongated bar magnets 4a, 4b and 4c enclosed therein.

The bar magnets 4a 4b and 4c are fixedly mounted, at an angle of approximately 90 to one another, on a stationary bar 5 secured on a shaft 5' fixedly supported at opposite ends thereof by the side walls 2a and 211, so that the magnetic fields of the former intersect to effect formation of magnetic brush bristles of the developer material upon the outer cylinder la. For this purpose, the magnet 41) is arranged to face the photoreceoptor surface 3a for formation of the magnetic brush bristles on the outer cylinder la at this position, while the magnets 4a and 4c are disposed in such positions that the developer material attracted onto the surface of the outer cylinder la is positively carried as the cylinder la rotates.

A stirring and scraping member 6 of a magnetic material in the configuration of a roller is rotatably provided below the toner dispenser l3 and adjacent to the surface of the outer cylinder 1a. The member 6 comprises a shaft 7 rotatably journaled in the side walls 2a and 2b of the developer housing 2 with a pair of friction rollers 8 suitably secured to the shaft 7 adjacent to the opposite ends thereof close to the inner surfaces of the side walls 2a and 2b and with many equally spaced con cave grooves cut around the shaft 7 between the friction rollers 8 so as to form a roller portion 9 with square edges ll corresponding to the number of the grooves 10 around the shaft 7 as shown in FIG. 2, thus upon rotation of the friction rollers 8, the roller portion 9 being rotated with the friction rollers 8.

Since the friction rollers 8 are adapted to press against the surface of the outer cylinder la at the opposite ends of the latter and disposed in a position to face the stationary bar magnet 40, or in the range of the magnetic force of the magnet 40, the roller portion 9 of the shaft 7 rotates in synchronization with the outer cylinder la as the latter revolves in association with the photoreceptor drum 3.

The outer periphery of the roller portion 9 should preferably be spaced away, to a slight extent, from the surface of the outer cylinder la to form a narrow gap therebetween, by which arrangement it is possible to prevent the developing material from generating heat due to compression between the roller portion 9 and the outer cylinder la.

The toner powder 17 contained in the toner tank 14 of the toner dispenser l3 provided in the upper portion of the developing device A is adapted to fall between the member 6 and the outer cylinder 1a through a suitable toner dispensing means l5 provided at the bottom portion of the toner tank 14 and through a slit [6 formed in the lowermost portion of the tank 14 immediately below the toner dispensing means 15.

By this arrangement, the outer cylinder 1a is adapted to rotate in the direction of an arrow B in association with the photoreceptor drum 3 rotating in the direction of the arrow A with the electrostatic latent image formed on the surface 3a of the drum 3 after charging and exposure, so that the developer material 12 attracted and raised by the outer cylinder la by the action of the magnet 4a is formed into magnetic brush bristles at the position of the magnet 4b facing the photoreceptor surface 3b for development of the latent image formed on the surface 3a.

After completion of the developing, the developing material remaining on the outer periphery of the outer cylinder in which rotates further in the direction of the arrow B and the fresh toner powder supplied through the slit 16 of the toner dispenser 13 are attracted by the magnetic force of the member 6 magnetized by the action of the stationary magnet 4C and rotating in the direction of an arrow C in synchronization with the rotation of the outer cylinder 1a.

In other words, the developing material 12 is positively attracted, from the outer periphery of the outer cylinder la, onto the roller portion 9 of the member 6 by the magnetic force concentrating at the square edges 11 of the roller portion 9 i.e., by the difference of strength of the magnetic force between the grooves 10 and the square edges 11. The developing material 12 thus attracted onto the roller portion 9 is dislodged toward the left of the member 6 in FIG. 1 by the centrifugal force arising from the rotation of the member 6, by the own weight of developing material 12 and also by the magnetic force decreasing with the rotation of the member 6 which is most strongly magnetized at the side thereof facing the magnet 40 with the least magnetization at the side remote from the magnet 4c, thus being subsequently stirred by the member 6.

Referring now to FIGS. 3 and 4 there is shown a modification of the embodiment of FIG. 1. In this modification, four elongated bar magnets 4a, 4b, 4c and 4d fixedly mounted, at an angle of approximately to one another. on the stationary bar 5 are enclosed in the rotatory outer cylinder la of the developing roller 1 with the magnet 4b facing the photoreceptor surface 3a for forming magnetic brush bristles on the outer cylinder 1a at this position.

The stirring and scraping member 6 is rotatably provided below the toner dispenser l3 and adjacent to the surface of the outer cylinder la in a position facing the magnet 4d. Similarly to the embodiment of FIG. 1, the member 6 comprises the shaft 7 rotatably journaled in the side walls 2a and 2b of the developing housing 2 with a pair of friction rollers 8 suitably secured to the shaft 7 adjacent to the opposite ends thereof close to the inner surfaces of the side walls 2a and 2b and with the friction rollers 8 engaging the outer periphery of the outer cylinder Ia under pressure for synchronous rotation therewith.

In this modification, the member 6 is provided. on the shaft 7 between the friction roller 8, with a roller portion 9 having four spiral projections 6a in the shape of screw which are disposed in such directions as to collect the attracted developing material in the middle portion C of the shaft 7 with the square edges 11 and the grooves 10 formed around the shaft 7 as shown in FIG. 4, which arrangement makes it possible to stirr the developing material upward and downward as well as leftward and rightward with high stirring efficiency.

The outer periphery of the roller portion 9 should preferably be spaced away from the outer cylinder la as in the embodiment in FIG. 1 for preventing the developing material from generating heat due to compression.

After completion of the developing, the developing material remaining on the outer periphery of the outer cylinder la which rotates in the direction of the arrow B is further carried, forming magnetic brush bristles on the cylinder la by the magnetic force of the magnets 4c, part of the which developing material falls downward by its own weight after passing over the magnet 40 due to decrease of the magnetic force, and subsequently formed into brush bristles by the action of the magnet 4d.

On the other hand, the roller portion 9 of the stirring and scraping member 6 which is adapted to rotate in the direction shown by the arrow C in synchronization with the rotation of the outer cylinder la is strongly magnetized since it faces the stationary magnet 4d, and magnetically attracts the falling developing material and the developing material formed into brush bristles on the cylinder la at the magnet 41].

The developing material thus attracted onto the roller portion 9 is positively held by the grooves 10 and the square edges 11 of the roller portion 9, and subsequently detached from the surface of the roller portion 9 by the decrease of the magnetic force and the centrifugal force as the roller portion 9 rotates, and also by the own weight of the developing material, consequently being sufficiently stirred by the member 6.

Since the fresh toner powder supplied through the slit 16 formed at the lowermost portion of the toner dispenser 13 is adapted to fall between the outer cylinder 1a and the stirring and scraping member 6, the fresh toner powder thus supplied is sufficiently stirred and mixed with the developing material being used, consequently making it possible to maintain the concentration of the developing material at a constant level.

It is needless to say that the stirring and scraping member 6 with the spiral projections 6a of the above modification is applicable to the embodiment in FIG. I, or the member 6 of the embodiment in FIG. 1 can also be applied to the above modification of FIG. 3.

It is to be noted here that the stirring and scraping member 6 of the present invention can be modified within the scope of the invention.

For example, the stirring and scraping member 6 which has been described in the embodiment of FIG. 1 as composed of the pair of friction rollers 8 and the roller portion 9 formed between the rollers 8 may be modified so as to be composed of the roller portion 9 only, without the friction rollers 8, in which case the roller portion 9 should be dimensioned so as to contact the surface of the outer cylinder 1a with the developing material thereon so that the portion 9 rotates with the rotation of the outer cylinder la.

Similarly, instead of the member 6 adapted to be driven by the outer cylinder la in contact therewith, any independent drive means may be employed for the rotation of the member 6, in which case the number of revolutions and direction of rotation of the member 6 can be altered as desired.

Furthermore, the member 6 may be composed of a plurality of equally spaced rollers 9a fixedly disposed on the shaft 7 between the friction rollers 8 as in FIG. 5, the plane of each of which rollers 9a extends at a certain angle relative to the axis of the shaft 7, so that the developing material 12 attracted thereto can be dislodged from the rollers 9a while being shaken rightward and leftward as the member 6 rotates with higher stirring efficiency.

Likewise, the member 6 may be in the form ofan axially splined roller 91; fixedly mounted on the shaft 7 as shown in FIG. 6.

As is clear from the above description, the stirring and scraping device of the present invention is provided with the rotatory member of magnetic material having many square edges on the outer periphery thereof, which member engaging the outer cylinder of the developing roller is adapted to scrape the remaining toner particles off the outer cylinder and also to stir efficiently the scraped toner particles during rotation of the member and the outer cylinder, so that disadvantages inherent in the conventional stirring vanes and scraping plates can be completely eliminated, thus resulting in compact size and light weight of the developing device with consequent reduction in cost.

Furthermore, according to the stirringand scraping device of the present invention, since the developing material is positively attracted to the member by the magnetic force concentrating on many square edges formed on the latter, and subsequently detached therefrom by the decreasing magnetic force and by the centrifugal force due to rotation of the member, and also by the own weight of the developing material, fatigue or deterioration of the developing material due to heat is advantageously avoided with uniform quality of copied images on the copied paper sheets, high scraping and stirring efficiency, and remarkably prolonged life of the developing material.

Although the present invention has been fully described by way of example with reference to the attached drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as included therein.

What is claimed is:

1. In a developing device for use in an electrophotographic copying apparatus which comprises a developing roller rotatably provided adjacent to a photoreceptor having a photoreceptor surface on the outer periphery thereof, said developing roller including a rotatable outer cylinder, and a plurality of stationary magnets enclosed in said outer cylinder and disposed in such positions that magnetic fields of said magnets intersect to attract and feed developing material onto said outer cylinder so as to form magnetic brush bristles on said outer cylinder for developing an electrostatic latent image formed on said photoreceptor surface into a visible toner powder image, a toner dispenser provided above said outer cylinder for replenishing said developing material with fresh toner powder, and a sump for said developing material provided below said developing roller, an improvement thereof for efficient stirring and mixing of said developer material with said fresh toner powder and scraping of said developer material off said outer cylinder after said developing comprises a stirring and scraping device composed of a rotary member provided below a toner dispenser and adjacent to an outer periphery of said outer cylinder, said rotary member which is provided with a plurality of grooves and square edges on an outer periphery thereof being adapted, during rotation thereof, to contact said developing material on said outer cylinder and to be magnetized by the magnetic force of said stationary magnets, said developing material being attracted onto said rotary member by magnetic force of the latter concentrating on said square edges and by a difference of strength of magnetic force between said square edges and said grooves, and subsequently dislodged from said rotary member by centrifugal force and decreasing magnetic force due to rotation of said rotary member and by the own weight of said developing material, during which process said developing material is stirred and mixed with said fresh toner powder from said toner dispenser.

2. A stirring and scraping device for developer material as claimed in claim 1, wherein said rotary member comprises a shaft with a pair of friction rollers secured at opposite ends thereof for engagement and synchronous rotation with said outer cylinder, said shaft being provided with a plurality of equally spaced grooves cut around said shaft between said friction rollers to form a roller portion having square edges corresponding to the number of said grooves around said shaft.

3. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft provided with a plurality of equally spaced grooves cut around said shaft to form a roller portion having square edges corresponding to the number of said grooves around said shaft, said roller portion being adapted to engage an outer periphery of said outer cylinder for synchronous rotation therewith.

4. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft with a pair of friction rollers secured at opposite ends thereof for engagement and synchronous rotation with said outer cylinder, said shaft being provided. between said friction rollers, with a plurality of spiral projections in the form of screw which are disposed in such directions as to collect the attracted developing material at a middle portion of said shaft, so as to form a roller portion having square edges with corresponding number of grooves around said shaft.

5. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft provided with a plurality of spiral projections in the form of screw which are disposed in such directions as to collect the attracted developing material at a middle portion of said shaft, so as to form 8 a roller portion having square edgeswith corresponding number of grooves around said shaft, said'roller portion being adapted to engage an outer periphery of said outer cylinder for synchronous rotation therewith.

6. A stirring and scraping device for developing material as claimed in claim I, wherein said rotary member is adapted to be driven by an independent drive means.

7. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft with a pair of friction rollers secured at opposite ends thereof for engagement and synchronous rotation with said outer cylinder, said shaft being provided with a plurality of equally spaced rollers fixedly disposed on said shaft between said friction rollers, each plane of said rollers being disposed to extend at a certain angle relative to an axis of said shaft so as to form a roller portion having square edges corresponding to the number of said rollers around said shaft.

8. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft provided with a plurality of equally spaced rollers fixedly disposed on said shaft, each plane of said rollers being disposed to extend at a certain angle relative to an axis of said shaft so as to form a roller portion haivng square edges corresponding to the number of said rollers around said shaft, said roller portion being adapted to engage an outer periphery of said outer cylinder for synchronous rotation therewith. I

9. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises an axially splined roller fixedly mounted on a shaft.

10. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises an axially splined roller integrally formed with a shaft.

11. A developing device for use in an electrophotographic copying apparatus which comprises a rotatable developing roller disposed adjacent a photoreceptor member for developing an electrostatic latent image formed thereon, a plurality of stationary magnets enclosed in said developing roller for attracting developing material and forming magnetic brush on the surface of said roller as it rotates, a magnetizable rotary member parallely provided adjacent said developing roller and positioned in the vicinity of one said magnets for said member to be magnetized, said rotary member being adapted to rotate with said developing roller for attracting the developing material on said roller surface whereby the attracted developing material is agitated and mixed by the rotational movement of said member.

12. A developing device as claimed in claim 11, wherein said magnetizable rotary member comprises a shaft provided with a plurality of grooves cut and square edges occurring alternatively for causing the difference in magnetic force therebetween for agitation and mixing of the developing material.

13. A developing device as claimed in claim 11 further comprises a toner replenishing means disposed above said rotary member and said developing roller for toner replenshed from said means to fall between said rotary member and said roller.

Claims (13)

1. In a developing device for use in an electrophotographic copying apparatus which comprises a developing roller rotatably provided adjacent to a photoreceptor having a photoreceptor surface on the outer periphery thereof, said developing roller including a rotatable outer cylinder, and a plurality of stationary magnets enclosed in said outer cylinder and disposed in such positions that magnetic fields of said magnets intersect to attract and feed developing material onto said outer cylinder so as to form magnetic brush bristles on said outer cylinder for developing an electrostatic latent image formed on said photoreceptor surface into a visible toner powder image, a toner dispenser provided above said outer cylinder for replenishing said developing material with fresh toner powder, and a sump for said developing material provided below said developing roller, an improvement thereof for efficient stirring and mixing of said developer material with said fresh toner powder and scraping of said developer material off said outer cylinder after said developing comprises a stirring and scraping device composed of a rotary member provided below a toner dispenser and adjacent to an outer periphery of said outer cylinder, said rotary member which is provided with a plurality of grooves and square edges on an outer periphery thereof being adapted, during rotation thereof, to contact said developing material on said outer cylinder and to be magnetized by the magnetic force of said stationary magnets, said developing material being attracted onto said rotary member by magnetic force of the latter concentrating on said square edges and by a difference of strength of magnetic force between said square edges and said grooves, and subsequently dislodged from said rotary member by centrifugal force and decreasing magnetic force due to rotation of said rotary member and by the own weight of said developing material, durIng which process said developing material is stirred and mixed with said fresh toner powder from said toner dispenser.

2. A stirring and scraping device for developer material as claimed in claim 1, wherein said rotary member comprises a shaft with a pair of friction rollers secured at opposite ends thereof for engagement and synchronous rotation with said outer cylinder, said shaft being provided with a plurality of equally spaced grooves cut around said shaft between said friction rollers to form a roller portion having square edges corresponding to the number of said grooves around said shaft.

3. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft provided with a plurality of equally spaced grooves cut around said shaft to form a roller portion having square edges corresponding to the number of said grooves around said shaft, said roller portion being adapted to engage an outer periphery of said outer cylinder for synchronous rotation therewith.

4. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft with a pair of friction rollers secured at opposite ends thereof for engagement and synchronous rotation with said outer cylinder, said shaft being provided, between said friction rollers, with a plurality of spiral projections in the form of screw which are disposed in such directions as to collect the attracted developing material at a middle portion of said shaft, so as to form a roller portion having square edges with corresponding number of grooves around said shaft.

5. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft provided with a plurality of spiral projections in the form of screw which are disposed in such directions as to collect the attracted developing material at a middle portion of said shaft, so as to form a roller portion having square edges with corresponding number of grooves around said shaft, said roller portion being adapted to engage an outer periphery of said outer cylinder for synchronous rotation therewith.

6. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member is adapted to be driven by an independent drive means.

7. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft with a pair of friction rollers secured at opposite ends thereof for engagement and synchronous rotation with said outer cylinder, said shaft being provided with a plurality of equally spaced rollers fixedly disposed on said shaft between said friction rollers, each plane of said rollers being disposed to extend at a certain angle relative to an axis of said shaft so as to form a roller portion having square edges corresponding to the number of said rollers around said shaft.

8. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises a shaft provided with a plurality of equally spaced rollers fixedly disposed on said shaft, each plane of said rollers being disposed to extend at a certain angle relative to an axis of said shaft so as to form a roller portion haivng square edges corresponding to the number of said rollers around said shaft, said roller portion being adapted to engage an outer periphery of said outer cylinder for synchronous rotation therewith.

9. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises an axially splined roller fixedly mounted on a shaft.

10. A stirring and scraping device for developing material as claimed in claim 1, wherein said rotary member comprises an axially splined roller integrally formed with a shaft.

11. A developing device for use in an electrophotographic copying apparatus which comprises a rotatable developing roller disposed adjacent a photoreceptor member for develoPing an electrostatic latent image formed thereon, a plurality of stationary magnets enclosed in said developing roller for attracting developing material and forming magnetic brush on the surface of said roller as it rotates, a magnetizable rotary member parallely provided adjacent said developing roller and positioned in the vicinity of one said magnets for said member to be magnetized, said rotary member being adapted to rotate with said developing roller for attracting the developing material on said roller surface whereby the attracted developing material is agitated and mixed by the rotational movement of said member.

12. A developing device as claimed in claim 11, wherein said magnetizable rotary member comprises a shaft provided with a plurality of grooves cut and square edges occurring alternatively for causing the difference in magnetic force therebetween for agitation and mixing of the developing material.

13. A developing device as claimed in claim 11 further comprises a toner replenishing means disposed above said rotary member and said developing roller for toner replenshed from said means to fall between said rotary member and said roller.

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