Abstract:
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.

Description:
BACKGROUND 
     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 “spitting” 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 “service station” 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 “spitting.” The waste ink is collected in a “spittoon” 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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective diagram of an inkjet printing mechanism embodiment of the present invention; 
     FIG. 2A is an exploded assembly diagram of a spittoon system useful in the printing mechanism of FIG. 1; and 
     FIG. 2B is a diagram of an alternative perspective of the spittoon system of FIG.  2 A. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates an inkjet printer embodiment of the present invention, and is referred to herein by the general reference numeral  100 . The printer  100  is representative of the many kinds of devices that use inkjets and spittoon reservoirs that can benefit from the present invention. For example, some inkjet-based fax and copier machines are included in alternative embodiments of the present invention. 
     The typical inkjet printer  100  includes a chassis  102  surrounded by a housing or casing enclosure  104 . Sheets of paper are typically fed through a print zone  106  for printing as they pass by an inkjet and carriage assembly. Printer  100  includes an inkjet cartridge  108 , a thermal printhead  110 , a service station  112 , a servicing region  114 , a sliding carriage guide rod  116 , a scanning axis  118 , and a printer controller  120  that receives print-job instructions from a host computer. The sliding carriage guide rod  116  mounted with chassis  102  allows an inkjet carriage  122  to slide back and forth across the print zone  106 . The scanning axis  118  is defined by the guide rod  116 . Carriage positional feedback information can be provided to printer controller  120  by an optical encoder reader (not shown) mounted to carriage  122 . Such typically reads an encoder strip that extends along the path of carriage travel. 
     The carriage  122  can be moved across guide rod  116  to a servicing region  114  inside casing  104 . A service station  112  within servicing region  114  is used to keep the inkjet cartridge clean and disposes of excess ink that is wiped off. It caps the inkjet cartridge to prevent drying of the ink inside and to block contamination by loose debris. 
     When inside print zone  106 , each paper sheet receives ink from ink-jet cartridge  108 . The cartridge  108  is sometimes called a “pen” by artisans. The inkjet cartridge  108  includes an ink reservoir (not shown) for storing a supply of ink. The inkjet cartridge  108  has a printhead  110 , with an orifice plate and a plurality of nozzles. The printhead  110  illustrated in FIG. 1 represents a thermal inkjet printhead, although other types of printheads may be used, such as piezoelectric printheads. 
     The outer surface of the orifice plate of the printhead  110  preferably lies in a common printhead plane. In the exemplary embodiment, such printhead plane extends substantially horizontally. 
     Here, only some of the pen servicing functions are discussed, e.g., spitting of the printhead  110 . A spittoon system like that illustrated in U.S. Pat. No. 6,132,026, issued to Bret K. Taylor et al on Oct. 17, 2000, can be incorporated in the service station  112 . 
     FIGS. 2A and 2B show a printhead  110  and a spittoon system  200  which can be separated from the service station and mounted independently on the printer chassis. 
     The spittoon system  200  is supported by the chassis  102  in the service region  114  within the printer casing  104 . The spittoon system  200  has a reservoir  202  for storing waste ink residues collected from the printhead  110  during servicing. The reservoir  202  has an opening  204  through which the ink residues from printhead  110  can drop inside. The reservoir  202  has vertical walls and a bottom  206  that parallels the plane in which the printhead  110  moves. 
     An inclined ramp  208  in the reservoir  202  extends down to an absorption foam  2100 . A plurality of capillary drains  212  are included in the surface of the ramp  208  to promote drainage to the absorption foam  210 . The ramp  208  has a first end  214  adjacent to a first side wall  216  of the reservoir  202  as well as the entranceway opening  204 , and a second end  218  (FIG. 2B) adjacent to the absorption foam  210  as well as the bottom wall  206 . The ramp  208  has a discharged region  220  close to the first end  214  for receiving ink residues (not shown) entering into the reservoir  202  from the printhead  110 . A space  222  is provided between the underside of ramp  208  and the bottom of reservoir  202 . 
     During spitting, the ink residues drop into the reservoir  202  and land on the ramp  208 . Gravity flows the ink residues down the ramp  208  toward the absorption foam  210 . The capillary drains  212  create a capillary action, which assists the flow of the ink residues to the absorption foam  210 . The ramp  208  preferably has a smooth surface, to promote ink drainage. The absorption foam  210  can be Polyester absorbent felt. The absorption of the inks that have reached the absorption foam  210  helps draw even more ink down the ramp  208 . 
     Eventually the absorption foam  210  will saturate. When this happens, ink flowing down the ramp  208  will spill over the bottom edges of the ramp and is collect underneath. Such ink will dry and make for more room underneath the ramp. So it helps if the ramp  208  is made of very thin sheet material. In alternative embodiments of the present invention, the ramp  208  can be flat bottomed or round channeled. 
     Embodiments of the present invention, in general, run excess ink down a ramp in a spittoon reservoir to a sponge. When the sponge fills, further excess ink is allowed to run down and collect under to ramp to dry. Such prevents the growth of dried ink pillars that can interfere with inkjet operation and clear, clean printing.