Patent Application
20060102032
The present invention relates generally to printing apparatuses, and more particularly, to a heating system for a printing apparatus.
Many printing apparatuses such as computer printers, graphic plotters, copiers, and facsimile machines employ inkjet printing technology. Inkjet printing typically produces images by ejecting tiny ink droplets onto the print media, such as paper. Many of the inks used in inkjet printing are solvent-based, e.g. water-based. However, there are some major problems associated with solvent-based inks. The ink-saturated media may become distorted or wavy, thereby causing a phenomenon called paper “cockle.” Furthermore, if the ink is not properly dried before the printed medium comes into contact with the starwheels positioned on the exit side of the print zone, the wet ink will transfer onto the starwheels then redeposit again onto the printed medium causing tracking. Thus, the solvent must be vaporized or absorbed into the media within a reasonable amount of time after printing.
To facilitate the drying of solvent-based inks in high-speed inkjet printers, several drying techniques have been employed. One technique is convection heating, wherein a heated gas is blown onto the printed medium. Another technique is radiant heating by applying infrared energy to the printed media. A third common heating technique is conductive heating by advancing the printed media around a heated roller or over a heated platen. The conventional heating set-ups often require additional components that add bulkiness to the printers and the corresponding control systems for achieving uniform heating are complicated and costly to install. Furthermore, many conventional heating systems, particularly convection heating systems, are thermally inefficient because they require a large amount of energy consumption. Some heating systems, such as radiant heaters, poses fire hazard and safety problems.
Accordingly, there exists a need for a printing apparatus having a compact and efficient heating system that is relatively inexpensive to install.
A printing apparatus with capability for drying printed media is disclosed. The printing apparatus includes a print zone and a post-printing zone, an advancing mechanism for transporting a medium sequentially through the print zone and the post-printing zone along a media transport path, a print head for ejecting ink onto the medium at the print zone during printing operation, and a heating system for drying the printed medium. The heating system includes a plurality of thermoelectric modules positioned in the post-printing zone. Alternatively, the thermoelectric modules may be positioned in the print zone. Each thermoelectric module has a heat-rejecting surface and a cooling surface. The heat-rejecting surface of each thermoelectric module is positioned to face the printed medium to be dried.
The advantages and features of the present invention will become apparent from the detailed description when read in conjunction with the drawings.
The present invention provides a printing apparatus with a heat generator for drying a printed medium. In the following description of the exemplary embodiments, the printing apparatus is an inkjet printer. However, it should be understood that the heat generator may be incorporated in any other printing apparatus employing solvent-based ink.
A printer may have several cartridges, but for convenience, only one is shown. A platen 18 is positioned below the ink cartridge 17 for supporting the print medium M during the passage of the medium through the print zone 11 and the post-printing zone 12. The platen 18 has an upper surface 18a that faces the ink cartridge 17. Primary output roller assembly 19 works in conjunction with a first starwheel 20 to advance the printed medium from the print zone to a post-printing zone 20. Secondary output roller assembly 21 works in conjunction with a second starwheel 22 to advance the printed medium from the post-printing zone 12 to a collection tray or another treatment zone. In order to prevent the ejected ink in the liquid phase from spreading on the medium and to prevent the printed medium from being distorted, a heating system 23 is arranged in the post-printing zone to facilitate ink drying immediately after printing. The heating system 23 is mounted on the post-printing region of the platen's upper surface 18a, which is between the primary and secondary output roller assemblies 19, 21.
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The thermoelectric modules 24 are small, very light and relatively silent solid state devices that function as heat pumps. As an example, each thermoelectric module 24 may be 4 mm thick, 6 mm in width and 6 mm in length. The size of the thermoelectric modules may be adjusted in accordance with the heating temperature needed for drying and the space available in the printer.
In the above embodiments, the heating system 23 is installed in the post-printing zone 12. However, it is also useful to have heat applied in the print zone 11 of the printer. Heating in the print zone will reduce ink migration that occurs during printing and in the first few fractions of a second after printing. The thermoelectric modules 24 described above may be installed in the section of the platen 18 that is in the print zone 12, in the same manner described for the embodiment of
The heat generator of the present invention is compact and can be installed at a relatively low cost. Furthermore, the heat generator of the present invention could apply heat to the printed media in a cost-efficient manner.
It is intended that the embodiments contained in the above description and shown in the accompanying drawings are illustrative and not limiting. It will be clear to those skilled in the art that modifications may be made to these embodiments without departing from the scope of the invention as defined by the appended claims.
