1. Field of the Invention
The present invention relates generally to inkjet printing mechanisms, and more particularly to a spittoon system for handling waste inkjet ink that has been discharged from an inkjet printhead during a nozzle clearing, purging or xe2x80x9cspittingxe2x80x9d routine.
2. Background of the Invention
Inkjet printing heads eject controlled sprays of ink onto a page while printing. Each such printhead has very small nozzles through which drops of various colored ink are fired. To print a typical image, the printhead is moved back and forth across a page, while ejecting patterns of ink drops. Conventional printheads use piezo-electric and thermal printhead technology. For instance, thermal ink ejection mechanisms are shown in U.S. Pat. No. 5,278,584 issued to Brian J. Keefe et al on Jan. 11, 1994 and U.S. Pat. No. 4,683,481, issued to Samuel A. Johnson on Jul. 28, 1987.
In thermal inkjet systems, barrier layers, ink channels and vaporization chambers are positioned between a nozzle orifice plate and a substrate layer. Such substrate layer typically includes linear arrays of heater elements, such as resistors, to heat ink inside the vaporization chambers. The instantaneous heating causes ink droplets to be ejected from the corresponding nozzle. By selectively energizing the resistors as the printhead moves across the page, the deposited ink can be precisely patterned to form particular text and graphic images.
A xe2x80x9cservice stationxe2x80x9d mechanism is typically included in each printer chassis for routine printhead maintenance. Such service stations usually include a capping system to seal the printhead nozzles from debris and to prevent drying of the ink inside the nozzles. Some caps are designed to help with ink priming, such as by being connected to a pumping unit that draws a vacuum on the printhead.
During operation, any clogs in the printhead can be periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as xe2x80x9cspitting.xe2x80x9d The waste ink is collected in a xe2x80x9cspittoonxe2x80x9d reservoir included in the service station.
Most service stations have a rubber wiper to wipe off excess ink, paper dust and other debris from the printhead surface. The wiping action can be done by moving the printhead across the wiper, the wiper across the printhead, or by moving both the printhead and the wiper.
Recent research has focused on improving the ink itself to improve the clarity and contrast of the printed image. Quicker, more waterfast printing with darker blacks and more vivid colors, pigment-based inks have been developed. Such pigment-based inks have a higher solid content than the earlier dye-based inks, and results in a higher optical density for the new inks. Both types of ink dry quickly. Such inkjet printing mechanisms produce high quality images on plain and specialty coated papers, transparencies, fabric, etc.
Unfortunately, the combination of small nozzles and quick-drying ink makes modern printheads more susceptible to clogging, e.g., from dried ink, minute dust particles, paper fibers, and solids within the new inks themselves.
Pillars of dried ink can grow up inside conventional ink spittoons to eventually contact the printhead. Such pillars resembling stalagmites can interfere with printhead movement, reduce print quality, and promote clogging of the inkjet printhead nozzles. Such stalagmites can grow to completely bridge across the narrow openings of some spittoons, and eventually close the spittoon opening. So prior art spittoons are made wide enough to prevent such bridging. But such extra width necessitates increasing the overall printer width.
A tapered screw spittoon system is disclosed in U.S. Pat. No. 6,213,583, issued to Patrick J Therien on Apr. 10, 2001. Such describes a tapered screw rotatably mounted in a reservoir of the spittoon. Ink residues are discharged onto a part of the tapered screw. When the screw is turned, ink residues are carried towards an exit in the reservoir wall, and squeezed out. This circumvents any ink residue stalagmite built-up and allows more efficient spittoon reservoir geometries.
Such complex mechanisms to deal with spittoon clogging add unnecessarily to the design, manufacturing, and expense of an inkjet printer. Less complex ways of dealing with the stalagmite build-up problem are needed to produce more affordable and more reliable printers.
Briefly, an inkjet waste ink handling system embodiment of the present invention includes a spittoon reservoir for collecting waste ink dropped from an inkjet printhead, and a ramp within the spittoon reservoir having an upper end that receives any ink dropped in and a lower end to which gravity conveys such ink. In this way, pillars of dried ink are prevented from accumulating.
According to a second embodiment of the present invention, a method for handling excess ink dropped from in inkjet printhead is provided. Firstly, excess ink is dropped from an inkjet printhead onto a top end of a ramp. Subsequently, the method uses gravity to flow said excess ink down to a bottom end of said ramp. In this way, pillars of dried ink are prevented from accumulating.
According to another embodiment of the present invention, an ink-jet printer includes an inkjet printhead that can discharge waste ink needing disposal, a spittoon reservoir located at a point under those that can be visited by the inkjet printhead and providing for collection of any waste ink dropped from the inkjet printhead, and a ramp within the spittoon reservoir having an upper end to receive any ink dropped in and a lower end to which gravity conveys such ink. The printer also includes a sponge disposed within the spittoon reservoir and adjacent to said lower end of the ramp and providing for collection of any ink that travels down the ramp. The sponge contacts the bottom end of the ramp and wicks in any ink traveling down toward it. The printer further includes an area disposed under the ramp for collecting and drying any ink not absorbed by the sponge and a capillary system disposed in the ramp and providing motivation for any ink on the ramp to move to the sponge. In such a printer, pillars of dried ink are prevented from accumulating.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which description illustrates by way of example the principles of the invention.