Abstract:
A method and system for a vacuum and ink manifold usable in a maintenance station of an ink jet printer, including at least one printhead maintenance cap, a pump generating negative pressure, a waste accumulator, and a manifold. The waste accumulator is designed specifically for the combination of dye and pigment inks to maintain the combined waste ink in a transportable fluid state.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to maintenance stations for ink jet printing apparatus. 
     2. Description of Related Art 
     Ink jet printers have at least one printhead that directs droplets of ink towards a recording medium. Within the printhead, the ink may be contained in a plurality of channels. Energy pulses are used to expel the droplets of ink, as required, from orifices at the ends of the channels. 
     In a thermal ink jet printer, the energy pulses are usually produced by resistors. Each resistor is located in a respective one of the channels, and is individually addressable by current pulses to heat and vaporize ink in the channels. As a vapor bubble grows in any one of the channels, ink bulges from the channel orifice until the current pulse has ceased and the bubble begins to collapse. At that stage, the ink within the channel retracts and separates from the bulging ink to form a droplet moving in a direction away from the channel and towards the recording medium. The channel is then re-filled by capillary action, which in turn draws ink from a supply container. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. No. 4,849,774. 
     A carriage-type thermal ink jet printer is described in U.S. Pat. No. 4,638,337. That printer has a plurality of printheads, each with its own ink tank cartridge, mounted on a reciprocating carriage. The channel orifices in each printhead are aligned perpendicular to the line of movement of the carriage. A swath of information is printed on the stationary recording medium as the carriage is moved in one direction. The recording medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to the width of the printed swath. The carriage is then moved in the reverse direction to print another swath of information. 
     The ink ejecting orifices of an ink jet printer need to be maintained, for example, by periodically cleaning the orifices when the printer is in use, and/or by capping the printhead when the printer is out of use or is idle for extended periods. Capping the printhead is intended to prevent the ink in the printhead from drying out. The cap provides a controlled environment to prevent ink exposed in the nozzles from drying out. 
     A printhead may also need to be primed before initial use, to ensure that the printhead channels are completely filled with the ink and contain no contaminants or air bubbles. After significant amounts of printing, and at the discretion of the user, an additional but reduced volume prime may be needed to clear particles or air bubbles which cause visual print defects. Maintenance and/or priming stations for the printheads of various types of ink jet printers are described in, for example, U.S. Pat. Nos. 4,364,065; 4,855,764; 4,853,717 and 4,746,938, while the removal of gas from the ink reservoir of a printhead during printing is described in U.S. Pat. No. 4,679,059. 
     The priming operation, which usually involves either forcing or drawing ink through the printhead, can leave drops of ink on the face of the printhead. As a result, ink residue builds up on the printhead face. This ink residue can have a deleterious effect on the print quality. Paper fibers and other foreign material can also collect on the printhead face while printing is in progress. Like the ink residue, this foreign material can also have deleterious effects on print quality. 
     The 717 patent discloses moving a printhead across a wiper blade at the end of a printing operation so that dust and other contaminants are scraped off the orifice before the printhead is capped, and capping the printhead nozzle by moving the printer carriage acting on a sled carrying the printhead cap. This eliminates the need for a separate actuating device for the cap. The 938 patent discloses providing an ink jet printer with a washing unit which, at the end of the printing operation, directs water at the face of the printhead to clean the printhead before it is capped. 
     SUMMARY OF THE INVENTION 
     This invention provides a vacuum accumulator and ink manifold usable with a maintenance station for an ink jet printer. 
     The printer has one or more printheads that are primed by a negative pressure created by a vacuum pump. Ink is drawn from the one or more printheads into one or more printhead caps of the maintenance station. In various exemplary embodiments, the one or more printheads eject both pigment-based inks and dye-based inks. The pigment-based and dye-based inks are drawn through the one or more maintenance caps and connecting tubing into an ink manifold. In the ink manifold, both the pigment-based and dye-based inks are mixed before the mixed ink flows out of the ink manifold and into a waste ink container. By mixing the pigment-based and dye-based inks in the ink manifold prior to pumping the mixed ink out of the ink manifold and into the waste ink container, the moisture level of the mixed ink remains high. By keeping the moisture level high, the likelihood of any clogging or stoppage due to increased viscosity, or in the extreme, drying and caking of the mixed in ink, is reduced. 
     These and other features and advantages of this invention are described in or are apparent from the following detailed description of various exemplary embodiments of the systems and methods according to this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various exemplary embodiments of this invention will be described in detail with reference to the following figures, wherein like numerals represent like elements, and wherein: 
     FIG. 1 is a schematic front elevation view of an ink jet printer and a maintenance station according to this invention; 
     FIG. 2 is an exploded, perspective view of a first exemplary embodiment of a vacuum accumulator and ink manifold according to this invention; 
     FIG. 3 is a perspective view, with the cover in place, of the vacuum accumulator and ink manifold of FIG. 4; and 
     FIG. 4 is a perspective view of a second exemplary embodiment, with the cover in place, of the vacuum accumulator and ink manifold according to this invention. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     FIG. 1 shows a printer  10 , including one or more printheads  12 , shown in dashed line, fixed to an ink supply cartridge  14 . The ink supply cartridge  14  is removably mounted on a carriage  16 . The carriage  16  is translatable back and forth on one or more guide rails  18  as indicated by arrow  20 , so that the one or more printheads  12  and the ink supply cartridge  14  move concurrently with the carriage  16 . Each of the one or more printheads  12  contains a plurality of ink channels which terminate in nozzles  22  in a nozzle face  23  (both shown in dashed line). The ink channels carry ink from the ink supply cartridge  14  to the printhead nozzles  22 . 
     When the printer  10  is in a printing mode, the carriage  16  translates or reciprocates back and forth across and parallel to a printing zone  24  (shown in dashed line). Ink droplets are selectively ejected on demand from the printhead nozzles  22  onto a recording medium, such as paper, positioned in the printing zone, to print information on the recording medium one swath or portion at a time. During each pass or translation in one direction of the carriage  16 , the recording medium is stationary. At the end of each pass, the recording medium is stepped in the direction of arrow  26  for the distance or the height of one printed swath. U.S. Pat. Nos. 4,571,599 and Re. 32,572, each incorporated herein by reference in its entirety, provide a more detailed explanation of the printhead and the printing operation. 
     When the printer  10  is no longer in a printing mode, the carriage  16  travels to a maintenance station  1000  spaced from the printing zone  24 . With the one or more printheads  12  positioned at the maintenance station  1000 , various maintenance functions can be performed on the one or more printheads  12 . 
     As shown in FIG. 1, the maintenance station  1000  includes a one or more printhead caps  1010  that are engagable with the one or more printheads  12  to withdraw ink, debris and the like from the nozzles  22  of the one or more printheads  12 . The waste ink withdrawn from the ink jet printheads  12  by the printhead caps  1010  are expelled or withdrawn from the maintenance station  1000  through one or more tubes  63  into a waste ink manifold  100  by a vacuum pump  300 . 
     In various exemplary embodiments, the one or more printheads  12  eject both pigment-based inks and dye-based inks. One exemplary embodiment of a pigment-based ink is carbon-black based black ink. One exemplary embodiment of dye-based inks are the cyan, magenta and yellow colored inks commonly used in ink jet printers. However, it should be appreciated that the pigment-based and dye-based inks are not limited to these exemplary embodiments. It should also be appreciated that the printer can use a single printhead that ejects both pigment-based and dye-based inks, one or more printheads that eject only pigment-based inks with one or more printheads that eject only dye-based inks, or a one or more printheads, where each such printhead has a vast array of nozzles that eject only pigment-based inks, and another, spaced-apart array of nozzles that ejects only dye-based inks, or any combination of these or other types of printheads. 
     FIGS. 2 show a perspective view of a first exemplary embodiment of a waste ink manifold  100  according to this invention. In FIG. 3, a top of the waste ink manifold  100  surface  170  has been removed. The waste ink manifold  100  has two bottom surfaces  140  and  150 , a top surface  170 , a side surface  105  and a series of internal supports  160 . In addition, the waste ink manifold  100  has two inlet ports  110  and  120  and one outlet port  130 . The waste ink manifold  100  serves to add an additional volume, when necessary, to assist the active impulse vacuum which drives the ink flow through the maintenance station  1000  and out the one or more tubes. 
     An active impulse vacuum from the vacuum pump  300  drives the ink flow through the maintenance station  1000  and out through the one or more tubes  63 . Although a specific length is not critical for the one or more tubes  63  in various exemplary embodiments, a relative volume ratio of 3 to 1 between the volume of the tubing  63  and the waste ink accumulator  100  to a pinch portion on the tubes  63  from the maintenance station  1000  to the volume of the tubes  63  and the one or more printhead caps  1010  from the pinch point should be maintained in order to maintain adequate priming of the printhead. That is, the volume between the vacuum pump  300  and the pinch point including the volume of the tubes  63  and the waste ink accumulator  100  should be three times the volume between the pinch point and printhead caps including the volumes of the tubes  63  and the printhead caps  1010 . Therefore, the closer that the vacuum pump  300  is moved to the maintenance station  1000 , which reduces the relative length of the tubes  63  downstream of the pinch point, the larger the volume provided by the waste ink manifold  100  must be. In addition, the ink outflow from the maintenance station  1000  that is contained in the one or more tubes  63 , may be combined through a Y-channel connector before reaching the waste ink manifold  100 . Alternatively, the ink outflow from the maintenance station  1000  may be communicated to the waste ink manifold  100  without using the Y-channel connector between the maintenance station  100  and the waste ink manifold  100 . In any case, with or without the Y-channel connector, the appropriate lengths of the one or more tubes  63  and their relative flow volumes must be taken into consideration to maintain an active impulse vacuum in order to adequately prime the printhead  12 . This will also provide adequate ink flow through the printhead caps  1010  to the waste ink manifold. 
     Optionally, a manual prime button (not shown) is provided on the printer for actuation by a printer operator when the printer operator notices poor print quality caused by, for example, a nozzle that is not ejecting ink droplets. This manual priming activated by the manual prime button works substantially the same way as the automatic prime sequence described above, which is generally performed when the print cartridge is installed or any other sensed event which is programmed into the printer controller. The only difference is that the amount of lapse time is reduced after the pinch valve is opened to reduce the amount of waste ink sucked from the print cartridge and prevent reduced printing capacity per print cartridge. Occasionally, a manual refresh prime may not be sufficient to improve print quality. Therefore, the user or the printer controller  40  can invoke the initial prime procedures after one or more attempts using the manual refresh prime were made. For example, after two consecutive manual refresh prime attempts within a two minute period, the third attempt would be made by the printer controller at using the initial prime procedure. 
     After priming the one or more printheads  12 , waste ink tends to be left in the flowpath between the one or more cap  600  and the ultimate receptacle for the waste ink. As indicated above, this flowpath includes the one or more cap  600 , the one or more tubes  63 , the waste ink accumulator  100  and the pump  300 . During the time the waste ink remains in the flowpath between the one or more printhead caps  1010  and the ultimate waste ink receptacle, the volume liquid components of the pigment-based inks tend to evaporate. In other words, the pigment-based inks become more viscous. This makes transporting such pigment-based inks to the ultimate waste receptacle very difficult, or even impossible if a long period of time has passed. The waste ink accumulator  100  according to this invention avoids this problem by ensuring that all of the waste ink flows out of the printhead caps  1010  and through the one or more tubes  63  into the waste accumulator  100 . In particular, because both the pigment-based inks and the dye-based inks flow into the single waste accumulator  100  through the ports  110  and  120 , the pigment-based inks and the dye-based inks tend to combine in the waste ink accumulator  100 . By combining the two different types of inks, the combined or mixed pigment-based and dye-based ink, due to the additional fluids in the dye-based inks, tends to keep the combined waste ink in the waste ink accumulator  100  in a transportable fluid state. In particular, in various exemplary embodiments, the dye-based inks are water-based inks. Thus, the combined waste ink in the waste ink accumulator  100  tends to remain in the transportable aqueous solution. Because of the additional fluids in the combined ink, the combined or mixed ink does not dry out and is easily able to pass from the waste ink accumulator  100  and into the ultimate waste ink receptacle. 
     A baffle  160  is provided in the waste accumulator  100 , to ensure that a portion of the manifold is void of ink for the next prime cycle. In the event that some quantity of ink was not evacuated from the manifold, the baffle  160  provides an air pocket to provide the volume needed to stay as close to the 3:1 ratio required and described above. 
     In the first exemplary embodiment of the waste ink receptacle shown in FIGS. 2 and 3, the one or more tubes  63  from the maintenance station  1000  comprises two tubes  63 , each connected to one of the maintenance caps  1010 . In particular, these two tubes  63  are connected directly to the waste ink accumulator  100  through the ports  110  and  120 . 
     FIG. 4 shows a second exemplary embodiment of the waste ink accumulator  200  according to this invention. In the waste ink accumulator  200 , the multiports  110  and  120  incorporated into the waste accumulator  100  and connected by the multiple tubes  63  to the multiple printhead caps  1010  are replaced with a single inlet port  210  and one outlet port  230 . This single inlet port  210  is connected to a single tube  63 . The other end of this single tube  63  is connected to the outlet port of a multiple inlet port connector. The multiple inlet ports of the multiple inlet port connector are connected by the multiple tubes  63  of the maintenance station to the multiple printhead caps  1010 . One exemplary embodiment of a multiple inlet port connector is the Y-connector described above. One exemplary embodiment of the Y-connector when used with the maintenance station  1000  is described in greater detail in U.S. patent application Ser. No. 09/594,680 herewith an incorporated herein by reference in its entirety. 
     While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.