DE2837942A1 - MAGNETIC BRUSH DEVELOPMENT DEVICE - Google Patents

Description

AG FA-G EVAERT AG

" ³ ""CAMERA-WERK MUNICH

PATBNTABTBlLUNa

CW 2116.9 PB / MB 08/29/78

10-re-hh

Magnetic Brush Development Facility

The invention relates to a magnetic brush developing device in an electrophotographic copier according to the Characteristics of the main claim.

Development devices are known / in which the magnetic brush development roller is assigned a sharp-edged doctor blade is, which is arranged at a small distance from the roll surface and for a uniform thickness and ensures a smooth surface of the layer of toner-developer mixture adhering to the developing roller. Through the stripping process high shear and frictional forces occur between the developer and toner particles within the developer mixture which have a negative impact on the life of the developer mixture. This negative influence is greater, the more Magnetic brushes include an inking unit. Another disadvantage of the doctor blade used hitherto can be seen in the fact that to overcome the occurring between the doctor blade and developer mixture Frictional forces relatively high additional drive

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moments have to be applied.

The invention is therefore based on the object of avoiding the aforementioned disadvantages of previous wiping elements, in particular to create a magnetic brush development device, the stripping or smoothing device of which the Toner-carrier-development mixture protects to an increased extent.

To solve this problem, according to the invention as Abstreifbzw. Smoothing element a rotatably mounted smoothing roller is provided, Surprisingly, this extremely easy-to-implement measure already increases the toner-carrier mixture Dimensions spared, so that the life of the mixture can be significantly extended in an economical way. In addition This also reduces the gap between the smoothing roller and the toner-carrier mixture occurring frictional forces are significantly reduced, so that the magnetic brush developing rollers to be fed Drive torque can be reduced compared to conventional developing devices. Furthermore, the rotatable smoothing roller generates dust, as with a stationary one Squeegee occurs, largely avoided. Soiling and wear and tear of the stripping or smoothing element also occur no longer open.

Further advantageous features of the invention are the remaining subclaims in connection with the following claim

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28373.42 "

Referring to writing in which the invention based on Drawing is described in more detail. In the drawing, the single figure shows a section in a semi-schematic representation by a magnetic brush developing device of an electrophotographic Copier with smoothing rollers cooperating with the developing rollers.

In the figure, 1 is the copying drum otherwise electrophotographic copier not shown in detail designated. For developing the image on the photosensitive Surface of the copying drum 1 located electrostatic The charge image is designated as a whole with the reference number 2 on the circumference of the copying drum in a known manner Development device provided - This development device comprises a housing 3 which is fixed in a device Shaft 4 can be suspended and is articulated to the copying drum by means of pressure means, not shown, while maintaining a small distance. On the housing of the developing device mounted spacer rollers 5, which are supported in a known manner on the circumference of the copying drum 1 ,, sor ~ conditions for maintaining the desired distance between development = winding device and copying drum «,

Inside the housing 3 , a magnetic transport roller S, magnetic development rollers 7 and 8, a mixing roller 9 and guide plates 10 and 11 are arranged in a known manner.

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Formed tub 12 are dispensing brushes 13 and 14 mounted, which the toner in the tub through in the bottom of the Well 12 provided openings 15 through into the interior of the developing device in precisely dosed quantities. In this way, the toner-carrier mixture located inside the developing device becomes that due to development The toner portion removed from the electrostatic images is supplied again. Above the tub 12 is a Axis 17 is arranged pivotably mounted guide frame 16 into which a toner refill container 18 is inserted.

Each of the toner developing rollers 7 and 8 is a smooth roller 19 and 20, respectively, the respective smooth roller and the associated developing roller being axially parallel. To the To be able to vary the distance between the surface of the developing roller and the surface of the smooth roller to a small extent, the smoothing rollers 19 and 20 are more suitable, not closer illustrated manner in the direction perpendicular to the roll surface displaceably mounted. From the toner-carrier mixture = supply 21 transports the transport roller 6 in a known manner due to magnetic forces of attraction a constant Amount in the direction of the development roller 7, which also takes over this mixture layer due to magnetic forces " By rotating the developing roller in the direction indicated in the figure, the developer layer 22 is between Ent = winder roller 7 and the smooth roller 19 passed so that seen in the direction of rotation of the developer roller 7 behind the

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Smoothing roller 19 the layer 22 the desired, constant thickness and has smoothness. In the further course the developer layer contacts 22 the surface of the copying drum 1 carrying the electrostatic charge image, the developer layer Toner particles are withdrawn, which attach themselves imagewise to the drum surface due to electrostatic forces. A further development roller 8 is provided for optimum development of the charge image, with a smoothing roller again 20 ensures a constant thickness and smoothness of the developer layer. Then this is done on the developer roller adhesive toner-carrier mixture removed with the help of the edge 11 a of the guide plate 11 from the developer roller and over the The guide plate 11 is conveyed to the mixing roller 9, where it is enriched with toner via the toner metering device.

In the present exemplary embodiment, the smoothing rollers 16 and 20 are only because of their friction with the developer layer 22 rotated. However, it is also possible to provide a separate drive for the smoothing rollers 19 and 20, the smooth roller and the developing roller preferably having the same peripheral speed.

1 sheet of drawings

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e e r s e

ite

Claims (4)

AGFA-GEVAERTAG CAMERA-WERK MUNICH FATBNTABTKlUUNa CW 2116.9 PB / MB 29.08.78 10-re-hh claims 1. Magnetic brush developing device in an electrophotographic copier for developing a latent electrostatic charge image using developing powder contained in a memory, which is supplied to the carrier of the charged image by means of at least one magnetic brush developing roller, with an element for generating which is arranged at a distance from the developing roller a constant thickness of developing powder on the developing roller, characterized in that _(? 20 19) is seen as an element ~ a rotatably supported smoothing roll. 2. Magnetic brush developing device according to claim 1 " characterized in that the smooth roller is freely rotatable is stored and only of what passed it by Developing powder (22) is set in rotation., 030011 / 02- CW 2116.9 PB / MB 3. magnetic brush developing device according to claim 1 or 2, characterized in that the center distance between Developing roller and smooth roller is adjustable. 4. magnetic brush developing device according to claim 1 or 3, characterized in that the smoothing roller (19, 20) with the same peripheral speed as the developing roller is motor-driven.