1. Field of the Invention
The present invention concerns a device and a method for electrical charging of a transport belt for transporting recording media in a transfer printing region of an electrophotographic printer or copier device. The invention also concerns an associated blade-like contact element.
2. Description of the Related Art
In electrophotographic printers or copier devices, the transfer of a toner image from an the intermediate carrier (for example a photoconductor drum or a photoconductor belt) onto a the recording medium is referred to as transfer printing. The section of the printer or copier device at which the intermediate carrier and the recording medium are brought into contact with one another is referred to as a transfer printing region. In the transfer printing region, the intermediate carrier (for example the generated surface of a photoconductor drum) and the recording medium move with the same speed in the same direction while the toner is transferred from the intermediate carrier onto the recording medium.
A good print image on the recording medium can only be achieved when a uniform contact is produced between the recording medium and the intermediate carrier in the transfer printing region. A good and uniform contact between the recording medium and the intermediate carrier can be achieved with the aid of an electrostatically-chargeable transport belt on which the recording media lies and, adhering to this with electrostatic forces, is transported through the transfer printing region.
A device for transfer of a toner image with the aid of an electrostatically-chargeable transport belt is shown in German Patent Document DE 102 47 368.4 (not previously published), which is incorporated by reference into the present specification. In this device, the transport belt is charged with a charge whose polarity is different than the polarity of the charge of the toner image. This electrostatic charging of the transport belt has a two-fold function: on the one hand, it effects an electrostatic attraction of the recording medium to the transport belt and thus a secure guidance of the recording medium in the transfer printing region; on the other hand, it effects the transfer of the toner image from the intermediate carrier onto the recording medium.
Similar devices with electrostatically-charge transport belts are also known from U.S. Pat. No. 5,666,622, German Patent Document DE 195 01 544 A1 and U.S. Pat. No. 5,159,392. In these three documents, the transport belt is either charged via corona arrangements (what are known as corotrons) or via contact rollers. A corotron typically comprises one or more thin, gold-coated tungsten wires whose electrical potential is about 1000 V relative to a grounded housing, such that the air surrounding the wires is ionized.
However, corotrons have a number of serious disadvantages including, for example, the ozone formation due to the high charge voltage and the relatively complicated exchange of worn-our corotron wires. Moreover, the corotron wires are easily contaminated with dust, belt abrasion particles and toner particles, which leads to an irregular charge distribution on the transport belt. Locations with a lower transport belt charge lead to a less complete transfer of the toner onto the overlying the recording medium and thus to unwanted lightening, or fading, of the print image. The cleaning of the corotron wires is not only elaborate but also subjects the wires to a significant mechanical stress and shortens their lifespan.
Contact rollers also have a disadvantage in that they can become contaminated easily and thereby lead to an irregular charging of the transport belt. Moreover, they can not be directly arranged in the transfer printing region because they would interfere with the uniform arrangement of the recording medium on the intermediate carrier. Nevertheless, in order to achieve a sufficient charge of the transport belt in the transfer printing region, a certain current must flow at the contact point from the contact roller and transport belt to the transfer printing region. Therefore, the conductivity of the transport belt may not be too low, which represents a disadvantageous limitation for the selection of the transport belt material used.
The present invention provides a device and a method for charging a transport belt in a printer that enables a uniform charge of the transport belt in the transfer printing region and requires less maintenance expenditure.
This is inventively achieved via a device and a method in which a blade-like contact element is arranged transverse to the running direction of the transport belt and abutting on the belt. The contact element transfers an electrical charge to the transport belt. The blade-like contact element can be arranged on a carrier element that can be inserted into and extracted from the printer or copier.
Such a blade-like contact element can be arranged directly in the transfer printing region on the side of the transport belt facing away from the intermediate carrier, and therewith provides a reliable, uniform electrostatic charge of the transport belt in the transfer printing region. Since the transport belt continually drags against the blade-like contact element, the contact element is constantly cleaned. Due to the ability of the carrier element to be removed, the blade-like contact element is easily replaced during maintenance. The blade-like contact element is preferably fastened on the carrier element so that it can be detached, such that it can be easily exchanged as an expendable part.
For better understanding of the present invention, reference is made in the following to the preferred exemplary embodiment shown in the drawings which is 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 device and the method as well as such further applications of the invention as they are shown therein are viewed as typical present or future specialized knowledge of a competent average man skilled in the art.
The components of an electrophotographic printer that participate in the printed image generation are schematically shown in
A paper transport aggregate 18 is also schematically shown in
Finally, a cleaning unit 42 for cleaning of the photoconductor drum and a fixing unit 44 for fixing the toner image onto the paper are shown in
The transport belt 20 serves for the transport of a paper sheet 46 (likewise shown in
As is to be learned from the schematic representation of
The paper transport aggregate 18, which was shown only schematically in
The paper transport aggregate 18 has a recess 50 into which the carrier element 48, with its attached contact element 34, can be inserted. The paper transport aggregate 18 with inserted carrier elements 48 is shown in
As is to be learned from
A first plug element 58 (see
The carrier element 48 and the blade-like contact element 34 are shown in an unassembled state in
A film 68 made from polyimide is adhered with a conductive adhesive onto the first section 60 of the angle plate. The film 68 has a thickness of 75 μm. Via interspersed carbon black particles, its volume resistance is reduced to a value that is between 102 and 109 Ωcm, preferably between 106 and 108 Ωcm. Its surface resistance is between 102 and 1012 Ω/sq, preferably between 1010 and 1012 Ω/sq.
The carrier element 48 has an essentially V-shaped cross section that is formed from a floor area 70 and a back wall 72. Small blocks 74 are arranged on the floor area 70 that are separated from the back wall 72 and with this respectively form a groove 76. Such a groove 76 can be recognized particularly well in
The groove 82 and the three grooves 76 form a recess into which the second section 62 of the blade-like contact element 34 can be inserted with positive fit. Both outer pressure pins 78 thereby press on the second section 62 of the blade-like contact element 34 and hold this in position. The center pressure pin 78 has a rounded tip and engages in the gap 66 in the second section 62 of the blade-like contact element 34, whereby it exerts pressure on the lower edge of the gap 66 in the representation of
A notch 84 is located in the web 80, into which notch 84 a guide section 86 on the blade-like contact element 34 engages when it is inserted into the recess of the carrier element 48. The guide section 86 and the notch 84 thereby help to find the correct position upon insertion of the blade-like contact element 34 into the recess of the carrier element 48.
Upon insertion of the blade-like contact element 34 into or, respectively, upon extraction of the same from the recess of the carrier element 48, the blade-like contact element can be gripped at the recurved sections 64. The blade-like contact element 34 is an expendable part and can be easily exchanged in the manner specified here and without the assistance of tool [sic]. In particular the exchange of the blade-like contact element is made easier in that the carrier element can simply be extracted from and inserted back into the printer or copier (in the shown exemplary embodiment from the paper transport aggregate 18 of such a one).
Electrical contacts (not shown) that contact the second section 62 of the angle plate when this is inserted into the recess of the carrier plate 48 are located in the groove 82. A current flow from the plug element 58 over the angle plate and the film 68 onto the transport belt is ensured via these contacts.
Although a preferred exemplary embodiment is shown and described in detail in the drawings and in the preceding specification, this should be viewed as purely exemplary and not as limiting the invention. It is noted that only the preferred exemplary embodiment is shown and described, and all variations and further modifications that presently and in the future lie within the protective scope of the invention should be protected.
Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
Number | Date | Country | Kind |
---|---|---|---|
102 53 698 | Nov 2002 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP03/11487 | 10/16/2003 | WO | 00 | 10/23/2006 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2004/046830 | 6/3/2004 | WO | A |
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195 01 544 | Jul 1995 | DE |
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Number | Date | Country | |
---|---|---|---|
20070041755 A1 | Feb 2007 | US |