Patent Application
20190263152
This application relates generally to a transfer belt unit of a toner-based printer, and more particularly to a transfer belt unit that uses platens in place of transfer rollers.
Document processing devices include printers, copiers, scanners and e-mail gateways. More recently, devices employing two or more of these functions are found in office environments. These devices are referred to as multifunction peripherals (MFPs) or multifunction devices (MFDs). As used herein, MFP means any of the forgoing.
Toner-based print engines of MFPs utilize a transfer belt unit (TBU) as part of the printing function. Toner is selectively attracted onto one or more photoconductive drums of an electrostatic process unit (EPU) in accordance with an image to be printed. The transfer belt transfers the toner from the photoconductive drums onto the paper, after which the transferred toner is then fused by heat onto the paper and delivered to a tray for retrieval by a user.
In black and white printers, a single photoconductive drum is used, while in color printers four or more photoconductive drums are used. Each photoconductive drum successively places toner of a particular color, such as yellow, magenta, cyan, or black, onto the transfer belt in accordance with the image to be printed. After the transfer belt has passed each photoconductive drum, the transfer belt has the entire image to be printer which is then transferred to the paper and fused to the paper by heat.
In order to transfer the toner between a photoconductive drum and the transfer belt, the transfer belt is electrically charged and brought within close proximity to the photoconductive drum so that toner from the photoconductive drum is attracted to the transfer belt. To maintain positional accuracy of the transfer belt relative to the photoconductive drum, a transfer roller is placed against the transfer belt opposite to the photoconductive drum. Each transfer roller ensures that the transfer belt is close enough to the photoconductive drum to allow most, if not all, of the toner from the photoconductive drum to move onto the transfer belt.
However, transfer rollers require periodic maintenance as bearings can wear or become clogged with stray toner. Also, because each transfer roller has a fixed diameter, the placement of multiple transfer rollers in a color printer places design constraints on the printer which must accommodate all of the transfer rollers. Smaller transfer rollers can reduce design constraints. However, smaller transfer rollers have surfaces with greater arcs than larger transfer rollers. Smaller transfer rollers can reduce the area of the transfer belt that is immediately proximate to each photoconductive drum, which also has an arced surface, which can affect the effectiveness of the transfer of toner from the photoconductive drum to the transfer belt.
Various embodiments will become better understood with regard to the following description, appended claims and accompanying drawings wherein:
In an example embodiment, a system and method for printing includes a transfer belt configured to transfer toner from a photoconductive drum of a toner-based printer to a paper. A transfer platen positions at least a portion of the transfer belt to be in proximity to the photoconductive drum.
In another more limited example embodiment, the system and method further includes a plurality of transfer platens, each associated with a corresponding photoconductive drum of an associated electrostatic process with each electrostatic process unit including a distinct color of toner.
In another more limited embodiment, the system and method includes a transfer platen that is substantially fixed in a non-rotatable position.
In another more limited embodiment, the system and method includes a transfer platen including electrically conductive foam.
In another more limited embodiment, the system and method includes a transfer platen comprised of a low friction conductive top layer over the electrically conductive foam.
The systems and methods disclosed herein are described in detail by way of examples and with reference to the figures. It will be appreciated that modifications to disclosed and described examples, arrangements, configurations, components, elements, apparatuses, devices methods, systems, etc. can suitably be made and may be desired for a specific application. In this disclosure, any identification of specific techniques, arrangements, etc. are either related to a specific example presented or are merely a general description of such a technique, arrangement, etc. Identifications of specific details or examples are not intended to be, and should not be, construed as mandatory or limiting unless specifically designated as such.
In toner-based electro-photographic printers, toner is picked up by a magnetic developer roller in an electrostatic process unit, or EPU, from a toner hopper. The magnetic developer roller rotates towards a photoconductive drum onto which an electric charge has been applied in accordance with a desired image to be printed, and toner from the magnetic developer roller is selectively transferred to the photoconductive drum. The toner is then transferred from the photoconductive drum to paper via a transfer belt and fused with the paper to form a printed page.
In black and white printers, a single photoconductive drum is used, while in color printers four or more photoconductive drums are used. Each photoconductive drum successively places toner of a particular color, such as yellow, magenta, cyan, or black, onto the transfer belt in accordance with the image to be printed. After the transfer belt has passed each photoconductive drum, the transfer belt has the entire image to be printer which is then transferred to the paper and fused to the paper by heat.
In order to transfer the toner between a photoconductive drum and the transfer belt, the transfer belt is electrically charged and brought within close proximity to the photoconductive drum so that toner from the photoconductive drum is attracted to the transfer belt. To maintain positional accuracy of the transfer belt relative to the photoconductive drum, a transfer roller is placed against the transfer belt opposite to the photoconductive drum. Each transfer roller ensures that the transfer belt is close enough to the photoconductive drum to allow most, if not all, of the toner from the photoconductive drum to move onto the transfer belt. Transfer belts are part of a removable unit called a transfer belt unit (TBU) that can include the transfer belt and transfer rollers.
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The transfer platens 304 can be any suitable shape, for example semicircles as illustrated. Advantageously, transfer platens 304 can be shaped so as to substantially reduce the amount of space required in the TBU. For example, not only are the semicircles half the height of rollers, but they can be partially hollow. Also, semicircles use less material than full circles and do not require the bearings, which results in a substantially reduce weight of the transfer platen 304 when compared to standard transfer rollers. Further, because transfer rollers need to rotate to perform the required function, transfer rollers have geometries that are limited to cylinders of different sizes. Because transfer rollers and photoconductive drums 306 are both cylinders, there is a limit to what forces the transfer rollers can exert on the transfer belt 302 to bring the transfer belt 302 into proximity of the photoconductive drum 306 to effect efficient toner transfer. By comparison, transfer platens 304 can use geometries suitably configured to optimize toner transfer from the photoconductive drums 306 to the transfer belt 302. For example, the transfer platens 304 can be shaped to allow for larger or smaller contact areas as well as differently shaped contact profiles with the transfer belt 302 and photoconductive drums 306.
Further, unlike transfer rollers, transfer platens 304 have no moving parts, and therefore do not require bearings and other structures that can wear out, become clogged, or otherwise require maintenance. Because transfer platens 304 do not require bearings, transfer platens 304 can be used to replace more costly transfer rollers and associated bearings.
The shape of the transfer platens 304 can be select to optimize toner transfer from each photoconductive drum 306 to the transfer belt 302. In an embodiment, each transfer platen 304 is identically shaped. In an embodiment, the transfer platens 304 can be different shapes. In an embodiment, each transfer platen 304 can be independent of the other transfer platens 304. In an embodiment, one or more transfer platens 304 can be connected together or manufactured as a common unit.
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In light of the foregoing, it should be appreciated that the present disclosure significantly advances the art of transfer belt units for toner-based printers. While example embodiments of the disclosure have been disclosed in detail herein, it should be appreciated that the disclosure is not limited thereto or thereby inasmuch as variations on the disclosure herein will be readily appreciated by those of ordinary skill in the art. The scope of the application shall be appreciated from the claims that follow.
