Abstract:
A printhead apparatus for filtering ink which includes an elongate open-ended trough having a bottom wall and opposing end walls and opposing side walls attached to the bottom wall, an ink exit port attached to the bottom wall between the opposing end walls and side wall, a filter member disposed in the open-ended trough between the end walls and the side walls and an elongate cover assembly attached to the end walls and the side walls covering the trough defining a filter chamber containing filter element, the cover assembly containing an ink inlet valve and a gas outlet valve. The device is disposed between an ink cartridge and an ink jet pen containing one or more printheads and is activated automatically when a new ink cartridge is installed on the pen thereby removing unwanted air and gas bubbles from the filter chamber and providing gas free ink to the pen and one or more printheads.

Description:
FIELD OF THE INVENTION 
     The invention relates to ink jet printers and in particular to a filter tower structure for attachment to a permanent or semi-permanent ink jet pen. 
     BACKGROUND OF THE INVENTION 
     During the lifespan of an ink jet printhead, air or gas bubbles develop in the ink and coalesce into larger bubbles. As the bubbles form and coalesce, they tend to accumulate in filter areas and ink feed channels of the ink jet 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 significantly affect printhead performance by causing misfiring or ink flow blockages. 
     A primary source of air or gas bubbles in the ink feed port of an ink jet pen 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 pen. 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 pen. Some of the air or gas bubbles which make there way into the ink flow channels of the pen are removed from the printhead through the ejection orifices, however, a portion of the air or gas bubbles finds its way back through the ink feed paths into the ink filter area of the pen. 
     Priming the pen by ejecting ink from the printhead may remove air or gas bubbles from the printhead itself, however, there may still be a substantial amount of air in the filter area of the pen or cartridge. 
     An object of the invention is to provide an apparatus and method with improves the operation of an ink jet pen. 
     Another object of the invention is to provide an apparatus and method for filtering ink for an ink jet printer. 
     Another object of the invention is to provide a filtration and air removal system which can be easily connected to an ink jet pen. 
     Still another object of the invention is to provide a method for filtering ink and removing air from the filter device of an ink jet printer. 
     Another object of the invention is to provide method for connecting an ink filtration system to an ink jet pen which simplifies the manufaturing steps thereof. 
     SUMMARY OF THE INVENTION 
     With regard to the foregoing and other object and advantages, the invention provides an apparatus for filtering ink for an ink jet pen which includes an elongate open-ended trough having a bottom wall, opposing end walls and opposing side walls attached to the bottom wall, a filtered ink exit port attached to the bottom wall between the opposing end walls and side walls, a filter element disposed in the open-ended trough between the end walls and the side walls and an elongate cover assembly attached to the end walls and the side walls covering the trough defining a filter chamber containing the ink filter element. The cover assembly of the apparatus contains an ink inlet valve and a gas outlet valve. 
     In another aspect the invention provides an ink jet printer which includes one or more permanent or semi-permanent printheads on an ink jet pen. One or more removable ink cartridges are attached to the pen, each cartridge containing an ink feed port having an ink flow path in flow communication with the one or more printheads and containing a bellows device for removing air or gas bubbles which accumulate in the ink flow path. At least one filtration and air removal system containing a filter chamber is attached to the pen between the cartridge and the pen for filtering ink flowing to the one or more printheads and for removing air and gas bubbles from filter chamber. 
     In yet another aspect the invention provides a method for filtering ink and removing air and gas bubbles from one or more ink feed ports of an ink jet pen. The ink jet pen contains one or more printheads disposed on one surface thereof and having an aperture on a second surface thereof for each printhead for flow of ink to the printheads. One or more removable ink cartridges is provided, each cartridge containing ink and having an ink feed port for supplying ink through the ink feed port to at least one printhead. At least one ink filtration and air removal system containing a filter chamber and a filter element in the filter chamber for filtering ink flowing from the one or more cartridges to the one or more printheads is provided. Each filtration and air removal system contains an ink inlet device, an ink inlet port, an air outlet device, an air outlet port and a filtered ink outlet port. The ink outlet ports are connected to the pen so that each outlet port is in flow communication with the aperture corresponding to the printhead. Upon attachment of each ink cartridge to the filtration and air removal system air is removed from the filter chamber. 
     An advantage of the ink filtration system of the invention is that it is configured to provide a filtered ink compartment having an air accumulation space therein for accumulating, coalescing and channeling unwanted air or gas bubbles in order to effectively remove such unwanted air or gas bubbles from the ink flow paths of the pen and ink cartridge. Removal of unwanted air or gas bubbles from the ink flow paths is substantially automatically activated upon replacement of an ink cartridge without any other operator intervention. Unlike priming devices or methods, the device of the invention is adapted for removal of air or gas bubbles so that only a relatively minute quantity of ink is removed or wasted from the ink cartridge or ink supply port. By “relatively minute” means from about 0 to about 1 milliliter, preferably from about 0.1 to about 0.2 milliliters. Priming devices typically only remove air from the printhead and ink paths in the printhead itself and are not effective for removing air bubbles from the ink filter chamber. The present invention, as described below, provides a substantial improvement in the ability to remove air or gas bubbles from the ink filter chamber and provides a substantially improved ink filtration system. 
    
    
     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 to scale, wherein like reference numbers indicate like elements through the sews, and wherein: 
     FIG. 1 is a perspective view of a removable ink supply cartridge assembled to an or use in an ink jet printer; 
     FIG. 2 is a cross-sectional view of a filtration and air removal device according to the invention; 
     FIG. 3 is an exploded view in perspective of a filtration and air removal device according to the invention; 
     FIG. 4 is a cross-sectional view of a filtration and air removal device according to the invention assembled to a removable ink supply cartridge containing a gas removal bellows; 
     FIG. 5 is a perspective view of an ink jet pen and o-ring for attachment to a filtration and air removal device thereto according to the invention; and 
     FIG. 6 is an exploded view in perspective of a bellows gas removal device used in conjunction with a removable ink cartridge and a filtration and air removal device according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 1, there is shown, in perspective view, a replaceable ink cartridge  10  connected to a permanent or semi-permanent ink jet pen  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 pen  12  may be configured to contain a single cartridge  10  or may be expanded to hold multiple cartridges  10 . In the case of a single color ink cartridge  10 , the pen  12  typically contains a single printhead  14  on a side of the pen  12  opposite the cartridge connection side  16  thereof. In the case of multiple cartridges  10  or multicolor cartridges  10 , the pen  12  may contain multiple printheads  14 , typically three or four printheads  14 . 
     In high speed, high quality printing operations, it is preferred that the pen  12  be adapted to remove heat from the printhead  14 . This may be accomplished by constructing the pen  12  out of a heat conducting metal such as aluminum or zinc and/or by providing heat conducting fins  18  on the pen  12  to conduct heat away from the printhead  14  by conduction and/or convention. 
     With regard to the ink cartridge  10 , the cartridge  10  hag an upper portion  20  containing a handle  22  and a lower portion  24 . A vacuum chamber and bellows device (which will be described in more detail below) is preferably disposed in the lower portion  24  of the cartridge  10 . 
     An important feature of the invention is an ink filtration and air removal system  30  shown in cross-sectional view in FIG.  2 . The ink filtration and air removal system  30  includes an ink feed needle valve assembly  32  and a gas removal needle valve assembly  34  attached to the upper portion  36  of an elongate, sustantially rectangular filter cavity  38 . The filter cavity  38  is defined by the upper portion  36 , side walls  40 , end walls  42  and bottom portion  44 . An ink outlet port  46  is attached to the bottom portion  44  and is in flow communication with filtered ink in a filtered ink and gas removal chamber  48  of the filter cavity  38 , The outlet port  46  preferably contains barbs or palls  50  which are used to sealingly connect the filtration and air removal system  30  to an ink jet pen. 
     Upon connection of a removable ink cartridge with the filtration and air removal system  30 , ink and air or gas flow into an upper chamber  52  of the filter cavity  38  through an elongate ink needle  54  and ink inlet port  56  attached to the top portion  36 . Debris and impurities are removed from the ink in the upper chamber  52  by means of filter element  58  so that purified ink accumulates in the filtered ink and gas chamber  48 . Because the filter element  58  is not horizontally disposed in the filter cavity  38 , air or gas bubbles are caused to accumulate in a gas accumulation area  60  of the cavity  38  adjacent a gas removal needle valve assembly  62 . The gas removal needle valve assembly  62  contains an elongate gas removal needle  64  which is in flow communication with the gas accumulation area  60  by means of a gas removal port  66  which is formed in the upper portion  36  of the filter cavity  38 . 
     Details of a preferred filtration and air removal system  30  shown in FIG. 2 may be seen in an exploded view of the system  30  with further reference to FIG.  3 . As can be seen, needle valve assemblies  32  and  34  are preferably substantially the same. The assemblies  32  and  34  include the elongate needles  54  and  64  which are sealingly attached to the ports  56  and  66  by means of resilient sealing devices such as o-rings  70  and  72 . Valve springs  74  and  76  are disposed around elongate needles  54  and  64  between needle flanges  78  and  80  and spring urging devices  82  and  84 . The spring urging devices  82  and  84  carry cylindrical valves  86  and  88  having annular openings  90  and  92  therein for receiving the elongate needles  54  and  64  therethrough. Valve guides  94  and  96  are attached to the top portion  36  and contain valve travel stop ledges  98  and  100  which engage flanges  102  and  104  of the spring urging devices  82  and  84 . 
     In their closed positions, valves  86  and  88  are urged away from top portion  36  by springs  74  and  76  so that the valves  86  and  88  cover inlet holes  106  and  108  in elongate needles  54  and  64 . Upon attachment of an ink cartridge  10 , spring urging devices  82  and  84  are urged toward upper portion  36  thereby depressing springs  74  and  76  and lowering valves  86  and  88  to expose ink inlet hole  106  and gas outlet hole  108 . Upon removal of the ink cartridge  10 , the springs  74  and  76  again urge valves  86  and  88  away from the top portion  36  so that valves  86  and  88  again cover and seal ink inlet hole  106  and gas outlet hole  108 . 
     With reference now to FIG. 4, a partial cross-section view of an ink cartridge  120 , bellows chamber  122  and filtration and air removal system  124  is shown with the filtration and air removal system  124  being engagedly connected to the ink cartridge  120 . When the ink cartridge  120  and filtration and air removal system  124  are connected, ink supply port  126  and air or gas bubble removal port  128  engage needles  130  and  132 , respectively which in turn urge spring urging devices  134  and  136  containing valves  86  and  88  (FIG. 3) toward upper portion  138  of the filtration and air removal device  124 . Upon urging valves  86  and  88  downward, ink inlet hole  140  and gas outlet hole  142  of needles  130  and  132  respectively are uncovered so that the filter cavity  144  is connected in flow communication with the ink outlet port  126  of the ink cartridge  120  by means of ink needle  130 . Likewise, a gas accumulation area  146  is connected in flow communication with the air or gas bubble removal port  128  for flow of air and/or gas through gas outlet needle  132  into a bellows system chamber  122 . 
     In order to seal the ink supply port  126  of the ink cartridge  120  against flow of ink out of the cartridge adjacent ink needle  130 , ink supply port  126  preferably contains an elastomeric septum  150  which sealingly engages needle  130 . Likewise, air or gas bubble removal port  128  preferably contains a septum  152  for sealingly engaging needle  132 . Upon flow of ink into filter cavity  144 , the ink is filtered to remove particles and debris by a filter  154  and the purified ink flows a filtered ink chamber  156  for flow out of ink supply port  158  into the pen  164  (FIG.  5 ). 
     Connection of the filtration and air removal device  124  to an ink jet pen  164  (FIG. 5) may be effected by inserting the ink supply port  158  into an opening or aperture  166  in the pen  164 . In order to sealingly connect the ink supply port  158  with aperture  166 , an elastomeric bushing, collar or o-ring  168  may be inserted into the aperture  166  or disposed around the ink supply port  158  in a groove. In the case of an elastomeric bushing or collar, the ink supply port  158  may contain palls or barbs  170  (FIG. 4) for sealingly engaging the inside surface area of the collar or bushing and for forcing the outside surface area of a collar or bushing in close adjacency with the inside surface area  172  of aperture  166 . The o-ring  168  is preferably made of an elastomeric material, including, but not limited to, natural rubber, synthetic rubber, polyurethane foam, silicone and the like, provided the material selected for the collar is resistant to the ink and effectively forms a seal to prevent ink or air leakage therethrough. Other means may be used to seal the connection between the ink supply port  158  and the aperture  166  in carrier  164  including, but not limited to, the use of adhesive with or without the use of a collar, bushing or o-ring  168 , and/or thermoplastic welding of the filtration and air removal device  124  to the pen  164 . 
     An exploded view of a preferred bellows system  200  is shown in FIG.  6 . The bellows system  200  includes a vacuum chamber  202  which is defined by a bottom portion  204 , side portions  206  and  208 , end portions  210  and  212  and a top edge portion  214 . An urging device  216  is disposed in the cavity  202  and a seal member  218  is attached along the top edge portion  214  to seal the vacuum chamber  202 . 
     The urging member  216  is preferably a resilient leaf spring device which is disposed in the chamber  202 , preferably in an initially compressed state, between the bottom portion  204  and the seal member  218 . The purpose of the urging member  216  is to urge the seal member  218  in a direction away from the bottom portion  204  of the chamber  202  upon connection of the bellows system  200  with an ink filtration and air removal system  30  as described above with reference to FIGS. 2 and 3. A wide variety of urging members  216  may be used, including but not limited to coil springs and resilient elastomeric open cell foam materials. Useful elastomeric foam materials include, but are not limited to, unfelted ether or ester type polyurethane foams and open-cell polyolefinic foams. Such foam materials are described, for example, in U.S. Pat. No. 5,400,067 to Day incorporated herein by reference as if fully set forth. 
     The seal member  218  is preferably made of a flexible thin film material such as a low density polyethylene film, polypropylene film, cellophane, vinyl and the like which is attached to the top edge portion  214  of the chamber  202 . An air-tight seal is preferably formed between the seal member  218  and the top edge portion  214  of the chamber  202  by melting the seal member  218  around the perimeter of the chamber  202  and/or by use of adhesives. Other means such as clamp rings, etc. may be used to sealingly attach the seal member  218  to enclose the vacuum chamber  202  of the bellows device  200 . It is preferred that the seal member  218  by resilient so that it can be initially urged toward the bottom portion  204  of the chamber  202  thereby depressing the urging member  216  without tearing or excessive stretching of the seal member  218 . 
     The bellows system  200  also contains a vacuum release port  220  which is in flow communication with the chamber  202  by means of a gas flow channel  222 . The gas flow channel  222  preferably has a width of about  0 . 5  to about 3 millimeters and a height of about 0.5 to about 3 millimeters thereby providing an orifice for flow of gas into the vacuum chamber  202 . In order to provide a bellows system  200  having an initial subatmospheric pressure in the chamber  202  thereof, air is urged from the chamber  202  by depressing the seal member  218  and urging member  216  toward the bottom portion  204  of the chamber  202  and sealing the vacuum release port  220  with a port sealing device  224 . A preferred port sealing device  224  is an elastomeric septum which may be punctured by a needle-like device or needle  132  (FIG. 4) and which effectively seals around the circumference of the needle-like device after puncture thereof to substantially eliminate any air or gas leakage therebetween. 
     Air or gas may thus be introduced into the bellows system  200  by means of puncturing the port sealing device  224  thereby causing urging device  216  and seal member  218  away from the bottom portion  204  of the chamber  202  as the air or gas flows from vacuum release port  220 , through channel  222  into chamber  202 . Urging device  216  therefor causes a suctioning effect as the seal member  218  is urged upward and away from the bottom portion  204 . 
     As shown, the bellows system  200  preferably includes an elongate substantially rectangular vacuum chamber  202 . The chamber  202  preferably has a volume of about 1 to about 30 nL, preferably about 3 nL. The invention is not intended to be limited to the shape of the bellows device  200  as shown in FIG. 5 as other shapes may be used for the bellows device  200  such a cylindrical, spherical, oval and the like, provided the vacuum chamber  202  has sufficient volume for removal of air or gas bubbles from the ink feed port areas of an ink cartridge and pen. 
     After initially depressing the seal member  218  towards the bottom portion  204 , and sealing the vacuum release port  220  with the septum  224 , the entire bellows system  200  is attached to an ink cartridge  120  (FIG. 4) so that the side of the seal member  218  opposite the vacuum chamber  202  and urging device  216  is adjacent the lower portion  160  of the cartridge  120  (FIG.  4 ). The bellows system  200  may be removably connected to the lower portion  160  as by means of clips or may be permanently attached to the cartridge  120  by thermoplastic welding techniques or by use of adhesives. 
     It is preferred that ink flow to the pen  164  (FIG. 5) from the cartridge  120  be established before activating the bellows system  200  to remove air from the gas accumulation area  146  (FIG.  4 ). This may be accomplished in a variety of ways. For example, needle  130  may be slightly longer than needle  132  so that needle  130  is in ink flow communication with the cartridge  120  before needle  132  is in gas flow communication with bellows system  200 . Alternatively, the cartridge  120  may be tilted to engage needle  130  before engaging needle  132  while the cartridge  120  is being attached to the filtration and air removal system. 
     Having described various aspects and embodiments of the invention and several advantages thereof, it will be recognized by those of ordinary skills that the invention is susceptible to various modifications, substitutions and revisions within the spirit and scope of the appended claims.