Abstract:
A waste ink pad system includes a separate first and second pad of absorbent material, each pad having a hole which is blocked by the opposing pad. The rate of evaporation of volatile components from waste ink is reduced by introducing the waste ink into the waste ink pad system at an interface between the first and second pads through a sleeve inserted into one of the blocked holes.

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 much 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. No. 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 also 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 waste pad system and method of manufacturing a waste pad, usable with a maintenance station. 
     The printer has one or more printheads that are primed by negative pressure created by a vacuum pump. Ink is primed for 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 one or more maintenance caps, connecting tubing, ink manifold and finally deposited in a waste pad system. As the inks are deposited in the waste pad assembly, the fluid inks are absorbed and migrate through the waste pads before the waste ink dries. 
     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 a perspective view of a top waste pad of one exemplary embodiment, of the improved waste pad system of FIG. 4; 
     FIG. 3 is a perspective view of a lower waste pad of one exemplary embodiment, of the improved waste pad system of FIG. 4; 
     FIG. 4 is a perspective view of a waste pad formed by combining the waste pads of FIGS. 2 and 3; and 
     FIG. 5 is a perspective view of a waste pad system 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. No. 4,571,599 and U.S. Pat. No. 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 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 are expelled or withdrawn from the maintenance station  1000  through one or more tubes into a waste ink manifold  70  by a vacuum pump. 
     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. 
     The waste ink is then drawn from the waste ink manifold, by the vacuum pump, into a waste ink pad system  200  according to this invention. As shown in FIGS. 2-5, in various exemplary embodiments, the waste ink pad system  200  includes a tray  210  into which are placed one or more ink pads  100 . 
     FIGS. 2 and 3 illustrate one exemplary embodiment of a waste ink pad  100  useable with the waste ink pad system  200  according to this invention. In particular, FIGS. 2-4 show a single waste ink pad  100  that is created using a first waste ink pad  110  and a second waste ink pad  120 . In particular, in various exemplary embodiments, the first and second waste ink pads  110  and  120  are formed using a single waste pad in two different orientations. In particular, the first waste ink pad  110  shown in FIG. 2 is shown in a first orientation, while the second waste ink pad  120  shown in FIG. 3 is shown in a second orientation rotated 180° about a vertical axis relative to the orientation of the first waste in pad shown in FIG.  2 . 
     As shown in FIGS. 2 and 3, the first waste ink pad  110  has a central hole  114  formed roughly in the geometric center of the first waste ink pad  110 . The first waste ink pad  110  also includes a second hole  112  that is position roughly halfway between one of the corners of the first waste ink pad  110  and the central hole  114 . 
     Similarly, the second waste ink pad  120  includes a roughly centrally located central hole  122  and a second hole  124  that is located approximately halfway between the central hole  122  and one of the comers of the second waste ink pad  120 . In particular, as shown in FIGS. 2 and 3, and more easily in seen in FIG. 4, the holes  112  and  124  are generally position at diagonally opposite comers of the first and second ink pads  110  and  120 . Of course, it should be appreciated that, in actuality, the ink pads  110  and  120  are the same single waste ink pad in different orientations. 
     As shown in FIG. 4, the waste ink pad  100  is formed by placing the first waste ink pad  110  over and aligned with the second waste ink pad  120 . In this orientation, the central holes  114  and  122  generally align, while the second holes  112  and  124  are located in diagonally opposite comers of the waste ink pad  100 . In addition, when the first and second waste ink pads  110  and  120  are combined and aligned to form the waste ink pad  100 , as shown in FIG. 4, a central axis or interface  140  is formed by the interface between a top surface  126  of the second waste ink pad  120  and a bottom surface  116  of the first waste ink pad  110 . 
     Additionally, as shown in FIG. 4, a sleeve  130  is inserted into the second hole  112  of the first waste ink pad  110 . In particular, in various exemplary embodiments, the sleeve  130  is inserted through the second hole  112  and butts against the top surface  126  of the second waste ink pad. The sleeve  130 , the second hole  112  of the first waste ink pad and the top surface  126  of the second waste pad  120  define a chamber. 
     FIG. 5 is a perspective view of the waste ink pad system  200  incorporating the waste ink pad  100  according to this inventions. As shown in FIG. 5, the waste ink pad system  200  includes a tray  210  in which the waste ink pad  100  is installed. A top cover (not shown) of the waste ink pad system  200  fits over the tray  210  such that the sleeve  130  extends through the cover. The sleeve  130  can be connected to a tube  75 , connecting the waste ink pad system  200  to the vacuum pump, as shown in FIG.  1 . U.S. patent application Ser. No. 09/594,683 filed herewith and incorporated herein by reference in its entirety, describes the waste ink accumulator  100  in greater detail. Alternatively, the waste ink pad system  200  can be used in place of the waste ink accumulator  100 . 
     Because the sleeve  130  extends only through the first pad  110 , the sleeve  130  ensures the waste ink flowing into the waste ink pad system  200  is adequately humidified. As the waste ink flowing into the waste ink pad system  200  collects within the sleeve  130 , this waste ink begins to migrate through the first and second waste ink pads  110  and  120 . In particular, the waste ink migrates between the first and second waste ink pads  110  and  120  along the central axis or interface  140 . By concentrating the waste ink along the central axis or interface  140  between the top surface  126  of the second waste ink pad  120  and the bottom surface  116  of the first waste ink pad  110 , the volatile liquid portions of the waste ink are not able to rapidly evaporate from the waste ink. 
     Because the waste ink remains in a volatile liquid phase for a longer period time, the waste ink is able to flow through the first and second waste ink pads  110  and  120  along the central axis interface  140  for a longer period of time. This allows the waste ink to migrate much more deeply into the first and second waste ink pads  110  and  120  from the second hole  112  formed in the first waste ink pad  110 . Thus, by slowing the evaporation of the volatile liquids from the waste ink, the capacity of the first and second waste ink pads  110  and  120  to contain the waste ink increases. 
     Furthermore, by keeping the deposition region of the waste ink pad  100  around the sleeve  130  well humidified and/or, by keeping of the interior of the sleeve  130  well humidified, premature drying and caking of the waste ink is reduced, and optimally, is kept to a minimum. 
     In the past, failure to keep the deposition region at which the waste ink is introduced into conventional waste ink pads adequately humidified has caused the waste ink to dry and crust immediately upon being deposited into the conventional waste ink pads. By crusting over the point of deposition, the waste ink prevents additional waste ink from entering into or migrating throughout the waste ink pads. As a result, only a small portion of the capacity of the conventional waste ink pads usable to hold waste ink is actually used. Thus, in the conventional waste ink pads, the entire volume of the conventional waste ink pads is ineffectively and inefficiently used. In contrast, in the waste ink pad system  200  according to this invention, because the waste ink remains in a liquid form for a substantially longer time, a substantially larger portion of the waste ink capacity of the waste ink pad  100  becomes usable. 
     As indicated above, the first and second waste ink pads  110  and  120  shown in FIGS. 2 and 3 effectively form a single ink pad  100 . Additionally, the first and second waste ink pads  110  and  120  can be manufactured as a single item, by cutting the centrally located hole  114 / 122  and the hole  112 / 124  located between the centrally located hole  114 / 122  and one corner of the waste ink pad. These holes can be cut in a single manufacturing process. This provides a more efficient and effective manufacturing process. In particular, the holes are formed by punching out circular material from the single pad. Then, to form the waste ink pad system  200 , a first one of the single pads is installed in the ink tray  210  as the second ink pad  120  in the second orientation. Then, a second one of the single pads is installed into the tray  210  as the first waste ink pad  110  rotated 180° from orientation of the second ink pad  120  as installed in the tray  210 . 
     Additionally, placing the two openings  112  and  124  at diagonally opposite corners of the waste ink pad  100  further extends the efficiency and capacity of the waste ink pad system  200 . This occurs because the openings at diagonally opposite corners provide straightforward manufacturing and assembly reference points. 
     While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternative, 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.