Abstract:
A filter tower structure for removing air or gas bubbles from an ink jet printing structure which includes a filter tower attached to an ink reservoir for feeding ink from the reservoir to a printhead, the filter tower structure including a conduit having an interior in flow communication with the ink reservoir and the printhead and a tube having a first end in flow communication with the interior of the conduit and a second end in flow communication with a vacuum source, wherein activation of the vacuum source results in the application of a reduced pressure to the interior of the conduit such that air or gas bubbles are caused to flow into the tube and exit the conduit and ink from the reservoir is caused to flow into the conduit.

Description:
FIELD OF THE INVENTION 
     The invention relates to ink jet printers and in particular to a filter tower structure for removing air from permanent and semi-permanent printhead assemblies. 
     BACKGROUND OF THE INVENTION 
     During the lifespan of an ink jet printhead assemblies or “pens”, air or gas bubbles develop in the ink and coalesce into larger bubbles. As the bubbles form and coalesce, they tend to accumulate in the ink feed port, filter areas and ink feed channels of the pen. If the amount of air or gas bubbles increases significantly, performance of the pen may be affected. For disposable pens, air accumulation is not typically a significant problem. However, for longer life permanent or semi-permanent pens, and for high quality, high speed pens, substantial air or gas bubble accumulation may adversely affect printhead performance by causing misfiring or ink flow blockages. 
     A primary source causing air or gas bubbles in the ink feed port, between the printhead and ink cartridge, arises from the removal and connection of ink cartridges with the pen. If a spent ink cartridge is allowed to run dry of ink, air will fill the ink feed port connecting the cartridge to the carrier/printhead assembly. Even if the ink cartridge is not run dry of ink, a certain amount of air is introduced into the ink feed port each time the ink cartridge is connected and/or disconnected from the carrier/printhead assembly. Some of the air or gas bubbles which make their way into the ink flow channels of the pen are removed from the printhead through ejection orifices, however, a portion of the air or gas bubbles under the action of buoyancy may migrate back through the ink feed paths into the ink feed port in the connection between the pen and the ink cartridge. 
     Priming the pen by ejection of ink may remove air or gas bubbles from the printhead itself, however, there may still be a substantial amount of air in the ink feed port due to cartridge replacement. This air is effectively trapped between the pen and the ink cartridge in the connection port connecting the cartridge to the pen assembly. 
     An object of the invention is to provide an apparatus and method for removing air and gas bubbles from an ink jet pen. 
     Another object of the invention is to provide a device for removing a substantial quantity of air from an ink feed port. 
     Still another object of the invention is to improve the operation of a permanent or semi-permanent pen. 
     SUMMARY OF THE INVENTION 
     With regard to the foregoing and other objects and advantages, the invention provides a filter tower structure for an ink jet printer pen, the filter tower structure including an elongate conduit having a first open end and a second end, the second end being closed by a filtering media and the conduit having an upper end thereof adjacent the filtering media in selective flow communication with a vacuum source. 
     In another aspect, the filter tower structure includes a filter tower attached to an ink reservoir for feeding ink from the reservoir to an ink jet pen. The filter tower includes a conduit having an interior in flow communication with the ink reservoir and the pen and a tube having a first end in flow communication with the interior of the conduit and a second end in flow communication with a vacuum source. Activation of the vacuum source results in the application of a reduced pressure to the interior of the conduit such that air or gas bubbles are caused to flow into the tube from the conduit and ink from the reservoir is caused to flow into the conduit. 
     In another aspect the invention provides an ink jet printing device including a carrier structure containing one or more permanent or semi-permanent printheads, a filtration and air removal system connected to the carrier structure in ink flow communication with the printheads, a replaceable ink cartridge containing an ink supply for supply of ink to the printheads. The ink cartridge is removably connected to the filtration and air removal system attached to the ink cartridge. The air removal device includes a conduit having an interior in flow communication with the ink cartridge and the printheads and a tube having a first end in flow communication with the interior of the conduit and a second end in flow communication with a vacuum source. 
     Activation of the vacuum source results in the application of a reduced pressure to the interior of the conduit such that air or gas bubbles are caused to flow into the tube from the conduit and ink from the ink cartridge is caused to flow into the conduit. 
     An advantage of the air or gas bubble removal system of the invention is that it is configured so that air or gas bubbles may be easily removed after a new ink reservoir has been installed on the printhead so as to avoid problems common to printing devices having replaceable cartridges. The present invention, as described below, provides a substantial improvement in the ability to remove air or gas bubbles from the ink feed port. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the invention will become apparent by reference to the detailed description when considered in conjunction with the figures, which are not no scale, wherein like reference characters indicate like elements through the several views and wherein: 
     FIG. 1 is a perspective view of a removable ink supply cartridge assembled to printhead carrier for use in an ink jet printer; 
     FIG. 2 is an exploded view in perspective of the cartridge and carrier of FIG. 1; 
     FIG. 3 is an exploded view in perspective showing a carrier and filter tower structure; 
     FIG. 4 is a front perspective view of a filter tower structure in accordance with a preferred embodiment of the invention; 
     FIG. 5 is a top plan view of the filter tower structure of FIG. 4; 
     FIG. 6 a side view of the filter tower structure of FIG. 5; 
     FIGS. 7-9 are cross-sectional side views showing a preferred method for priming a replaced ink cartridge in accordance with the invention; 
     FIG. 10 is a side view of another embodiment of a filter tower structure in accordance with the invention wherein the conduit has a top perpendicular to the cylindrical sides and the filter is a convex, dome shaped filtering media; and 
     FIG. 11 is a side view of another embodiment of a filter tower structure in accordance with the invention wherein the tube through which vacuum is applied to the tower structure is external to the ink flow path. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIGS. 1-3, there is shown, in perspective view, a pen  1  for use with an ink jet printer and having a replaceable ink supply cartridge  10  connected to a permanent or semi-permanent printhead carrier  12 . The ink cartridge  10  may contain a single color ink, such as black, cyan, magenta or yellow or may contain multiple colors of ink. The carrier  12  may be configured to attach to a single cartridge  10  or may be expanded to hold multiple cartridges  10 . In the case of a single color ink cartridge  10 , the carrier  12  typically contains a single printhead  14  on a side of the carrier  12  opposite the cartridge connection side  16  thereof. In the case of multiple cartridges  10  or multicolor cartridges  10 , the carrier  12  may contain multiple printheads  14 , typically three or four printheads  14 . 
     In high speed, high quality printing operations, it is preferred that the carrier  12  be adapted to remove heat from the printhead attached thereto. This may be accomplished by constructing the carrier  12  out of a heat conducting metal such as aluminum or zinc and/or by providing heat conducting fms  18  on the carrier  12  to conduct heat away from the printhead by conduction and convention. 
     The cartridge  10  has an upper portion  20  containing a handle  22  and a lower portion  24 . An outlet port  26  is located on bottom  28  of the lower portion  24  and is initially sealed as by a ruptureable membrane or a septum with a pre-pierced aperture. The membrane is ruptured by the filter tower  30  during installation of the cartridge  10  onto the carrier  12  when the cartridge  10  is fully seated on the carrier  12 . In its attached configuration, the filter tower  30  of the pen is in flow communication with ink within the cartridge  10  and the printhead  14  for providing an ink feed path for conducting ink from a reservoir within the cartridge  10  and for filtration of ink conducted from the cartridge  10  to the printhead  14 . 
     The filter tower  30  is fixedly or removably attached to the carrier  12  by inserting lower open end  38  into a port or opening  32  extending through the side  16  of the carrier  12  above and adjacent the printhead  14 , the opening  32  being in flow communication with the printhead. A seal such as O-rings, adhesives, elastomeric collars or the like is preferably provided to seal against leakage of ink through the junction of the tower  30  and the opening  32 . Likewise, a similar seal is also preferably provided to seal against leakage through the junction of the tower  30  and the port  26  of the cartridge  10 . 
     Turning to FIGS. 3-6, the tower  30  includes a conduit  34  preferably of substantially circular cross-section and having an a first open end  36  in flow communication with the port  26  of the attached cartridge and a lower open end  38  in flow communication with the printhead  14 . The conduit  34  is preferably continuous between its open ends and is preferably made of a material similar to that of the cartridge, such as a polymeric or plastic composition that is resistant and impermeable to ink. 
     The end  36  has a peripheral edge which may be perpendicular to the axis through the tower or is angled as best seen in FIG. 6, preferably at an angle a of from about 4 to about 70 degrees with respect to a longitudinal axis through the conduit  34  from the open end  36  to a second end  38 . A filter  40  made of a conventional filter media material is positioned adjacent the first end  36  for removing debris and impurities from ink traveling from the cartridge to the printhead through the conduit  34 . The conduit  34  preferably contains a tube  42  which is positioned along a sidewall of the conduit  34 , with its longitudinal axis parallel with the longitudinal axis of the conduit  34 . The conduit  34  preferably has a length of from about 4 mm to about 25 mm and a diameter of from about 3 mm to about 30 mm, it being understood that the conduit may be otherwise sized depending upon the dimensions of the cartridge, carrier and printhead and may have a variety of shapes including rectangular, oval, triangular and the like. 
     The tube  42  is preferably continuous between an upper open end  44  and a lower open end  46  and is preferably co-formed with the conduit  34 . The upper open end  44  is preferably located adjacent an uppermost portion  48  of the angled conduit  34  (FIG. 6) and the lower open end  46  is preferably located adjacent a lowermost end  49  of the conduit  34 . The tube  42  preferably has a length of from about 0.5 mm to about 100 mm and a diameter of from about 0.5 mm to about 4 mm when used with a conduit of the dimensions described above. The lower open end  46  is preferably in selective flow communication with a vacuum source, as at  50  (FIG.  7 ), preferably a low-pressure vacuum source operable at a range of pressure of from about 20 cm wc (water column) to about 500 cm wc, for evacuating air and other fluids (liquids and gasses) from the conduit  34 . 
     With reference now to FIGS. 7-9, there is shown a preferred method of installing and priming a replacement ink cartridge  10  after the used or empty cartridge  10  has been removed from the carrier. As shown in FIG. 7, the new cartridge having an ink reservoir containing an ink saturated foam  52  is installed on the filter tower and cartridge as by inserting the conduit  34  into the port  26  and rupturing a seal in the port  26 . A liquid tight connection is then made between the lower open end  46  of tube  42  and the low-pressure vacuum source  50 . This liquid tight connection may be accomplished by providing the tube  42  of sufficient length to extend to a convenient location on the carrier  12  so that end  46  is adjacent a pre-pierced septum and/or a check-ball valve (represented by reference numeral  58  in FIG. 9) in order to close end  46  of tube  42 . As will be noted (FIG.  7 ), the conduit  34  may contain a significant amount of air and a low volume of ink  54  prior to removal of air from conduit  34 . 
     In order to remove air from conduit  34  and to prime the pen, the vacuum source  50  is activated and a predetermined volume of air, such as from about 0.2 mL to about 8 mL, possibly mixed with ink, is removed from the conduit  34  via the tube  42  by applying a reduced or sub-atmospheric pressure to the end  46 . As air is removed from the conduit  34  the air is replaced with the same volume of ink from the newly installed cartridge  10 , which flows through the filter  40  into the conduit  34  as indicated by the arrows  56 . A reduced pressure is applied to continue to draw air from the conduit  34  and promote migration of ink into the conduit (FIG. 8) until the conduit  34  is primed and sufficiently void of air so as to function as desired (FIG.  9 ). The application of reduced pressure is then ceased and the tube  42  sealed as by plug or valve  58  operable with the source of vacuum. Verification of a sufficiently primed pen may be accomplished as by print tests and the like. If a print test fails to indicate a desirably operable pen, then the valve  58  may be opened and additional vacuum applied to reprime the pen. This repriming step may be repeated until the pen is desirably primed. 
     As will be appreciated, the invention advantageously enables the removal of air from the ink feed path after a new ink reservoir is installed so that the pen does not suffer disadvantageous effects common to pens of the type having replaceable ink reservoirs. 
     Turning now to FIG. 10, there is shown another embodiment of a filter tower structure having a conduit  60  with a first open end  62  opposite second open end  64  which may be positioned in flow communication with a printhead. The periphery of the first open end  62  of this embodiment is substantially perpendicular to an axis through conduit  60  from first end  62  to second end  64 . A convex, dome shaped filtering media  66  is attached to end  62 . A flow tube  68  is centrally located within the conduit  60  so that it is in flow communication with the uppermost portion  69  of domed filter media  66 . The tube  68  includes an upper open end  70  in flow communication with the upper most portion  69  of the filter  66  and a lower open end  72  which may be rendered in selective flow communication with a vacuum source in the manner previously described for the flow tube  42 . 
     FIG. 11 shows another filter tower structure in accordance with the invention which includes a conduit  74  having an angled first open end  76  adjacent which a filtering medium may be attached and a second open end  78  for positioning in flow communication with a printhead. A flow tube  80  having an open end  82  extends through an aperture  84  of the conduit  74 . The opposite end of the flow tube is in selective flow communication with a vacuum source  86  for applying vacuum to the conduit  74 . The aperture  84  is preferably positioned adjacent an uppermost portion  88  of the angled conduit  74 . 
     The foregoing description of certain embodiments of the invention has been provided for the purposes of illustration only, and it is understood that various modifications or alterations may be made without departing from the spirit and scope of the invention as set forth in the following claims.