Photocopying – Including fiber optics
Patent
1979-11-02
1982-08-17
Braun, Fred L.
Photocopying
Including fiber optics
118657, 118661, G03G 1500
Patent
active
043446949
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
Latent, electrostatic images are usually developed by means of developing apparatus equipped with so-called magnetic brushes. These devices include one or a plurality of magnetic rollers for transferring a magnetically attractable developer powder from a reservoir to the latent, electrostatic image. In order to obtain uniform development of the electrostatic image, it is necessary for the magnetic roller, which is used to transfer the developer powder to the image, to be covered with a uniform layer of powder at least in the area of the developing zone. However, such a uniform powder layer can be achieved only if a homogeneous magnetic field is present in the developing zone over the entire operating range of the magnetic roller. In particular, with high speed developing apparatus it is further necessary that a strong magnetic field be generated near the cylindrical surface of the magnetic roller to prevent the developer powder from being flung away at the high rotational speed of the cylinder. Moreover, the reaction time provided for development of the latent image has been steadily reduced as a result of the increased speed of movement of the image carrier.
One way to increase the speed is to increase the length of the developing zone. Such a device is disclosed in German Offenlegungsschrift No. 2,010,737 in which two directly adjacently arranged magnetic brush developing rollers are provided. By mutual interaction, the magnetic fields of these two magnetic brush developing rollers hold the developer substance in contact with the latent electrostatic image over an extended area. An enlargement of the effective developing zone is obtained thereby but requires additional expenditures and structures.
Additionally, German Offenlegungsschrift No. 1,572,348 discloses a developing apparatus in which the resulting brush has a rectangular cross section so that a sufficiently large contact or friction area is obtained with the surface of the photosensitive layer. This assures, at greater expense, that the toner or image powder, respectively, is deposited on the photosensitive layer in sufficient quantities and uniformly.
PROBLEM AND SOLUTION
It is the object of the invention to improve the development of latent electrostatic images with magnetizable developing substances and to attain, with the simplest means, an increase in the size of the developing zone, in order to be able to produce a high quality image. Furthermore, the magnetic rollers employed should have the lowest possible magnetic induction. This is accomplished by the present invention.
With the developing apparatus according to the invention, the brush surface of a given brush length is increased with simple means so that a uniform deposit of the developer particles is realized and an abrasive effect at the image surface is avoided.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic sectional view of the apparatus according to the invention;
FIG. 2 shows a detail of FIG. 1;
FIG. 3 is a detail of FIG. 2; and
FIG. 4 illustrates a second embodiment of the magnetic roller.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows in a schematic sectional view parts of an electrophotographic copier in which a photoconductive sheet 1 is fixed on a guide drum 3. The guide drum 3 rotates on an axis 5 and is mounted in a frame (not shown) of the machine for movement past the individual processing stations. The photoconductive sheet is initially charged in a charging station 7, is then photographically exposed in an exposure station 9 and then developed in a developing station 11. Then the image existing on the photoconductive sheet 1 is transferred to a receiving material 15 in a transfer station 13. After the transfer, the record carrier material is removed from the photoconductive sheet 1 by means of a removing corona 17 and is brought to a pressure fixing station 19 from where the record carrier material 15 is then transported by means of transporting rollers 21, 23 into a depository 25. The toner particles still remaining on the
REFERENCES:
patent: 3402698 (1968-09-01), Kojima et al.
patent: 3882821 (1975-05-01), Katayama et al.
patent: 3941469 (1976-03-01), Okamoto
patent: 4018187 (1977-04-01), Abbott et al.
patent: 4136637 (1979-01-01), Snelling
Zelazny, Joseph, "Flexible Roll Shell", Xerox Disclosure Journal, vol. 1, Nos. 9 and 10, Sep./Oct. 1976, p. 13.
Sanders, K., "Magnetic Brush Developer", IBM Technical Disclosure Bulletin, vol. 19, No. 4, Sep. 1976, pp. 1410 and 1411.
Braun Fred L.
Olympia Werke AG
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