The preferred embodiment concerns a developer station for a printer or copier with a rotating developer roller to which toner particles can be supplied, which toner particles accumulate on the surface of the developer roller and are subsequently transferable to a further rotating roller or a continuous belt in a transfer zone. The preferred embodiment also concerns a method for this.
In electrographic printers or copiers, image development methods are used that ink electrostatic charge images on surfaces (for example charge images on a photoconductor) across an air gap or in direct contact with toner particles. These toner particles are located on a developer roller that transfers them directly onto a cylindrical photoconductor or a continuous belt, or they are transferred from the developer roller to a further roller or a continuous belt from which the charge image is then inked on the photoconductor as an intermediate image carrier. The toner image present on the intermediate image carrier is then transferred and fixed onto a print medium (for example paper) in the further course of the printing or copying process.
In order to obtain a high-grade print quality, a homogeneous layer structure of the toner particles on the developer roller is to be maintained as an important prerequisite. Small irregularities in the toner layer can already lead to quality loss in the print image, for example color shifts and brightness fluctuations.
The following print documents are referenced as relevant prior art: DE 101 52 892 A1, DE 31 18 995 A1, EP 0 394 228 B1 and WO 89/08285 A.
U.S. Pat. No. 5,234,786 describes a developer station with a smoothing device which smoothes a mixture made up of carrier particles and toner particles. The smoothing device contains a magnetic smoothing element which exerts a pressure on the mixture layer and smoothes this layer. The developer roller stands directly opposite a photoconductor roller as an intermediate image carrier and transfers toner particles onto the surface of the photoconductor roller to ink the latent intermediate image.
U.S. Pat. No. 5,845,183 describes developer stations in which the developer consists exclusively of toner particles and not of a mixture of toner particles and carrier particles. The smoothing device smoothes the layer consisting exclusively of toner particles on developer rollers.
It is an object to specify a developer station and a method that ensure or, respectively, ensures a high print quality.
In a developer station for a printer or copier, a rotating developer roller is provided having a mixture of toner particles and ferromagnetic carrier particles accumulated on a surface of the developer roller as a layer, and a transfer zone at which the toner particles are transferred away from the developer roller. A smoothing device is provided with a smoothing element arranged before the transfer zone, the smoothing element being charged with a mechanical tension in a rest state of the developer roller and designed such that it exerts a force on and over an entire width of the layer formed by the mixture of the toner particles and the carrier particles present on the developer roller and smoothes the layer before the transfer of the toner particles. Within the developer roller at least one magnet is provided. The smoothing element comprises a magnetizable material attracted toward said at least one magnet to create said mechanical tension.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the preferred embodiments/best mode illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated as would normally occur to one skilled in the art to which the invention relates are included.
According to one aspect of the preferred embodiment, an operating method is specified that ensures that a uniform toner layer is present in the transfer zone. The technical advantages that can be achieved with this method coincide with those described in the developer station.
The preferred embodiment can advantageously be used in electrographic printing or copying apparatuses whose recording methods for image generation are in particular based on the electrophotographic, magnetographic or ionographic recording principle. The printing or copying apparatuses can also use a recording method for image generation in which an image recording medium is directly or indirectly electrically energized, point by point. However, the preferred embodiment is not limited to such electrographic printing or copying apparatuses.
To better understand the present invention, reference is made in the following to the preferred exemplary embodiments presented in the drawings, which are described using specific terminology. However, it is noted that the protective scope of the invention should not thereby be limited since such variations and further modifications to the shown devices and/or the method, as well as such additional applications of the invention as they are indicated therein, are viewed as typical present or future expertise of a competent man skilled in the art. The Drawing Figures show exemplary embodiments of the invention.
Due to the magnetic field of the magnets 16 through 24, a magnetic brush forms in the radial direction of the developer roller 12 since the ferromagnetic carrier particles arrange and align along the magnetic field lines as a result of the force effect of the magnetic fields. An accumulate of carrier particles and toner particles adhering to them results on the surface of the developer roller 12 in the region of the outward-pointing poles of the magnets 16 through 24 (whose polarity can respectively alternate in the circumferential direction). Such a protruding accumulations of carrier particles and toner particles is designated as a magnetic brush due to the brush-like shape. The mixture made up of toner particles and carrier particles moves as well upon rotation of the developer roller 12 in the direction of the arrow P1.
A rigidly stationary housing wall 32 of the developer station 10 contains a scraper 32 which determines the layer thickness of the magnetic brush. A smoothing device 34 comprises a rigid mount 36 and a smoothing element 38. The mount 36 is firmly connected with the housing part 32. The smoothing element 38 is connected elastically or flexibly at the distal end of the mount 36. In the example according to
Instead of a magnetic smoothing element 38 in the form of a thin metal band, a non-magnetic metal band can also be used. It is advantageous when the contact force or the initial mechanical tension are generated with the aid of springs or an elastic element.
A further exemplary embodiment is presented in
The end of the smoothing elements 38, 40, 42 should be arranged optimally close to the transfer zone 30; the distal end of the smoothing element 38, 40, 42 should advantageously extend up to the gap between developer roller 12 and further roller 28. It is thereby ensured that, as a result of the inhomogeneity of the magnetic fields, irregularities in the magnetic brush can again form in the region of the transfer zone 30. The discharge of carrier particles and toner particles is additionally reduced by the smoothing element 38, 40, 42 arranged immediately before the transfer zone 30.
It is also advantageous when the respective smoothing element 38, 40, 42 has a low-wear or wear-resistant coating at least on the side facing towards the toner layer. Such a wear-resistant coating can be a hard-chrome plated coating, a ceramic coating, or a plasma coating. For example, a titanium oxide layer that is advantageously applied via a plasma coating can be provided as a wear-resistant coating.
A toner system without ferromagnetic carrier particles can also be used instead of the two-component mixture made of toner particles and ferromagnetic carrier particles. In this case, the smoothing device 34 also produces the formation of a homogeneous, smoothed toner carpet in the inking zone.
Although preferred exemplary embodiments are shown and described in detail in the drawings and in the preceding specification, these should be viewed purely as examples and not as limiting the invention. It is noted that only preferred exemplary embodiments are presented and described, and all variations and modifications that presently and in the future lie within the protective scope of the invention should be protected
Number | Date | Country | Kind |
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10 2006 031 876 | Jul 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2007/056720 | 7/4/2007 | WO | 00 | 12/18/2008 |
Publishing Document | Publishing Date | Country | Kind |
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WO2008/006747 | 1/17/2008 | WO | A |
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Number | Date | Country | |
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20090279922 A1 | Nov 2009 | US |