Abstract:
In one embodiment an ink pen for an inkjet printer includes: an ink filter chamber; a pressure regulator chamber downstream from the ink filter chamber along a path of ink flow through the pen; a pressure regulator in the pressure regulator chamber; a filter in the ink filter chamber; an inlet to the ink filter chamber upstream from the filter along the ink flow path; and an outlet from the ink filter chamber to the pressure regulator chamber downstream from the filter along the ink flow path such that ink flowing from the inlet to the outlet passes through the filter. In another embodiment a method implemented in an ink delivery system for an inkjet ink pen includes: chambering ink in the pen; filtering the chambered ink; and then regulating the pressure of filtered ink.

Description:
BACKGROUND 
     The physical size of an inkjet printer ink pen directly affects the size and cost of the printer. (An ink pen is also commonly referred to as an ink cartridge or an inkjet printhead assembly.) The bigger, higher performance inkjet pens used in some high end office printers require extensive structure and actuators to properly position the pens in the printer, enlarging both the size and the cost of the printer. The ink filtering and pressure regulating components in the ink delivery system in higher performance ink pens are some of the bulkiest components in the pen. These components are embedded in the body of the pen and, therefore, contribute to a large part of the pen size. By reducing the size of the ink filtering or the pressure regulating components, or both, the size of the pen may be significantly reduced. 
    
    
     
       DRAWINGS 
         FIG. 1  is a block diagram illustrating an inkjet printer. 
         FIG. 2  is a block diagram illustrating one exemplary embodiment of an ink pen. 
         FIG. 3  is an elevation view of one exemplary embodiment of an ink pen. 
         FIG. 4  is an exploded perspective view of the ink pen shown in  FIG. 3 . 
         FIG. 5  is a perspective view of the pen body in the ink pen of  FIGS. 3 and 4 . 
         FIG. 6  is an elevation section view of the ink pen shown in  FIGS. 3 and 4  taken along the line  6 - 6  in  FIG. 7 . 
         FIG. 7  is a plan section view of the pen body of the ink pen shown in  FIGS. 3 and 4  taken along the line  7 - 7  in  FIG. 6 . 
         FIG. 8  is an elevation view of one exemplary embodiment of a filter frame. 
         FIG. 9  is an elevation view of a conventional filter frame. 
         FIG. 10  is an elevation view of a conventional ink pen. 
     
    
    
     DESCRIPTION 
     Embodiments of the present invention were developed in an effort to reduce the size of a higher performance, “off axis” inkjet ink pen. Exemplary embodiments of the invention will be described, therefore, with reference to an off axis ink pen and an inkjet printer. Embodiments of the invention, however, are not limited to the exemplary ink pen or printer shown and described below. Other forms, details, and embodiments may be made and implemented. Hence, the following description should not be construed to limit the scope of the invention, which is defined in the claims that follow the description. 
     Referring to  FIG. 1 , inkjet printer  10  includes a printhead  12 , an ink supply  14 , a pump  16 , a print media transport mechanism  18  and an electronic printer controller  20 . Printhead  12  in  FIG. 1  represents generally one or more printheads and the associated mechanical and electrical components for ejecting drops of ink on to a sheet or strip of print media  22 . A typical thermal inkjet printhead includes a nozzle plate arrayed with ink ejection nozzles and firing resistors formed on an integrated circuit chip positioned behind the ink ejection nozzles. The ink ejection nozzles are usually arrayed in columns along the nozzle plate. Each printhead is operatively connected to printer controller  20  and ink supply  14 . In operation, printer controller  20  selectively energizes the firing resistors and, when a firing resistor is energized, a vapor bubble forms in the ink vaporization chamber, ejecting a drop of ink through a nozzle on to the print media  22 . In a piezoelectric printhead, piezoelectric elements instead of firing resistors are used to eject ink from a nozzle. Piezoelectric elements located close to the nozzles are caused to deform very rapidly to eject ink through the nozzles. 
     An ink chamber  24  and printhead  12  are often housed together in an ink pen  26 , as indicated by the dashed line in  FIG. 1 . Ink flows to printhead  12  from ink supply  14  through ink chamber  24 . Ink pens like ink pen  26 , which allow the ink to be replaced as it is consumed from a remote, refillable, ink supply  14 , are sometimes referred to as “off axis” pens. Ink chamber  24  represents generally one or more ink chambers  24  in pen  26  through which ink passes on its way to printhead  12 . For example, as described below, the ink may pass through a filter chamber and a pressure regulating chamber before reaching the printhead. Printer  10  may include a series of stationary ink pens  26  that span the width of print media  22 . Alternatively, printer  10  may include one or more ink pens  26  that are scanned back and forth across the width of media  22  on a moveable carriage. Media transport  18  advances print media  22  lengthwise past printhead  12 . For stationary pens  26 , media transport  18  may advance media  22  continuously past printhead  12 . For a scanning pen  26 , media transport  18  may advance media  22  incrementally past pen  26 , stopping as each swath is printed and then advancing media  22  for printing the next swath. 
     Controller  20  receives print data from a computer or other host device  28  and processes that data into printer control information and image data. Controller  20  controls the movement of carriage, if any, and media transport  18 . As noted above, controller  20  is electrically connected to printhead  12  to energize the firing resistors to eject ink drops on to media  22 . By coordinating the relative position of pen(s)  26  and media  22  with the ejection of ink drops, controller  20  produces the desired image on media  22  according to the print data received from host device  28 . 
       FIG. 2  is a block diagram illustrating one exemplary embodiment of an ink pen  26 . Referring to  FIG. 2 , ink is pumped into a filter chamber  30  in pen  26  from a separate ink supply (not shown) through an inlet  32 . Ink passes through a filter  34  in filter chamber  30  before flowing into a regulator chamber  36 . (Ink chamber  24  from  FIG. 1 , for example, may include a filter chamber  30  and a regulator chamber  36  from the embodiment of ink pen  26  shown in  FIG. 2 .) Ink flows from regulator chamber  36  to printhead  12  where it may be ejected on to print media as described above. In many inkjet printers, ink flows to the printhead at a slight negative pressure (vacuum) to control the free flow of ink through the ink ejection nozzles when the printhead is not activated. Without such negative pressure, ink may leak or “drool” from the nozzles. Hence, a pressure regulator  38  in chamber  36  maintains the pressure in chamber  36  within a desired range of negative pressures. A variety of different types of pressure regulators, well known to those skilled in the art of off axis inkjet printing, may be adapted for use in pen  26 . Pressure regulator  38 , therefore, represents generally any suitable pressure regulator. For example, the spring bag type pressure regulator used in the ink pens for the Edgeline Technology printing products marketed by Hewlett-Packard Company may be adapted for use as pressure regulator  38  in pen  26 . 
       FIGS. 3-7  illustrate one exemplary embodiment of an ink pen  40  that may be used as a pen  26  shown in the block diagrams of  FIGS. 1 and 2 .  FIG. 3  is an elevation view of the exterior of pen  40 .  FIG. 4  is an exploded perspective view of ink pen  40 .  FIG. 5  is a perspective view showing the internal design of the pen body and  FIGS. 6 and 7  are elevation and plan section views, respectively, of ink pen  40 . Referring first to  FIGS. 3-4  and  6 , pen  40  includes a lower exterior housing  42 , an upper exterior housing  44 , and a cover or cap  46 . The printheads (not shown) are housed in lower housing  42  so that printhead nozzle plates  48  ( FIG. 6 ) are exposed along the bottom of pen  40  for ejecting ink drops  50  ( FIG. 6 ) on to paper or other print media  52  ( FIG. 6 ). The body  54  of pen  40  is housed within upper and lower housings  42  and  44 , as best seen in the section view of  FIG. 6 . 
     Referring now to  FIGS. 4-7 , the exemplary embodiment of ink pen  40  shown is configured to receive and eject two different inks. Pen body  54  is divided lengthwise into units  56 A and  56 B by a central barrier  58 . The exploded perspective of pen  40  in  FIG. 4  is viewed looking into the inlet side of pen body unit  56 A (which is the outlet side of unit  56 B) while the detail perspective of pen body  54  in  FIG. 5  is viewed looking into the inlet side of pen body unit  56 B (which is the outlet side of unit  56 A). Ink flows through each pen body unit  56 A and  56 B to a separate printhead. When ink pen  40  is installed in a printer, ink inlet ports  60 A and  60 B are connected to an off axis ink supply and pumping system (not shown in  FIGS. 3-7 ), such as an ink supply  14  and pump  16  illustrated in the block diagram of  FIG. 1 . Ink is pumped through inlet ports  60 A and  60 B into corresponding filter chambers  62 A and  62 B, which are enclosed by a cover plate  63 A and  63 B ( FIG. 4 ). 
     A filter  64 A,  64 B is supported on a filter frame  66 A,  66 B in each filter chamber  62 A,  62 B. Each filter frame  66 A,  66 B is positioned in chamber  62 A,  62 B with an inboard face  67 A,  67 B facing central barrier  58  and an outboard face  68 A,  68 B. Each filter  64 A,  64 B is supported on both the inboard and outboard faces  67 A/ 68 A,  67 A/ 68 B of filter frame  66 A,  66 B. Thus, each filter chamber  62 A,  62 B is divided into two sub-chambers by filter  64 A,  64 B—an exterior/upstream sub-chamber  70 A,  70 B and an interior/downstream sub-chamber  72 A,  72 B. 
     Each ink inlet port  60 A,  60 B opens into the exterior sub-chamber  70 A,  70 B of filter chamber  62 A,  62 B. A passage  74 A,  74 B through barrier  58  to pressure regulator chambers  76 A,  76 B is located at one corner of each filter chamber  62 A,  62 B. An opening  78 A,  78 B in the corner of each filter frame  66 A,  66 B exposes each passage  74 A,  74 B to interior filter sub-chambers  72 A,  72 B. Ink pumped into exterior sub-chambers  70 A,  70 B through inlet ports  60 A,  60 B passes through filter  64 A,  64 B into interior sub-chambers  72 A,  72 B, and then through openings  78 A,  78 B and passages  74 A,  74 B into regulator chambers  76 A,  76 B. The flow of ink through pen unit  56 A from inlet port  60 A to regulator chamber  76 A is illustrated by arrow  80  in  FIG. 7 . An interior barrier  82  separates the A unit filter chamber  62 A from the B unit regulator chamber  76 B. An interior barrier  84  separates the B unit filter chamber  62 B from the A unit regulator chamber  76 A. 
     A pressure regulator  86 A,  86 B in each regulator chamber  76 A,  76 B controls the flow of ink from filter chamber  62 A,  62 B into chamber  76 A,  76 B through passage  74 A,  74 B, and out of chamber  76 A,  76 B through outlets  88 A,  88 B to the corresponding printhead. Each pressure regulator  86 A,  86 B includes, or is operatively coupled to, a flow control valve  89  ( FIGS. 6 and 7 ) that opens and closes each passage  74 A,  74 B in response to pressure changes in regulator chamber  76 A,  76 B. When ink is ejected from pen  40 , the ink supply in regulator chamber  76 A or  76 B (or both) is depleted and the pressure inside chamber  76 A,  76 B falls. As the chamber pressure falls below a predetermined low pressure threshold, pressure regulator  86 A,  86 B opens flow control valve  89  (or allows valve  89  to open if valve  89  is biased toward the open position), allowing ink from the pressurized filter chamber  62 A,  62 B to enter regulator chamber  76 A,  76 B. When enough ink has entered chamber  76 A,  76 B to raise the pressure to a predetermined high pressure threshold, pressure regulator  86 A,  86 B closes flow valve  89  (or allows valve  89  to close if valve  89  is biased toward the closed position) to stop the flow of ink into chamber  76 A,  76 B. The pressure regulators and flow valves mentioned above are well known to those skilled in the art of inkjet printing and, therefore, are not shown or described in detail. Although each pressure regulator  86 A,  86 B is depicted generally as including an expandable/collapsible bag  90 A,  90 B and an expanded rigid cover  92 A,  92 B, any suitable pressure regulator may be used. For example, and as noted above, the spring bag type pressure regulator used in the ink pens for HP&#39;s Edgeline Technology printers may be adapted for use as pressure regulators  86 A and  86 B in pen  40 . 
     It has been discovered that the size of an off axis ink pen can be substantially reduced by locating a filter chamber upstream from the pressure regulator chamber and moving the ink filter upstream from the pressure regulator, as shown in FIGS.  2  and  3 - 7 . In a conventional pen, in which ink is filtered downstream from the pressure regulator, the pressure available to move ink through the filter is limited to the pressure generated by the pumping action of the ink drop generator in the printhead, typically only 1-2 inches of water. This lower pressure requires a larger filter to allow the desired flow of ink to the printhead. When the ink is filtered upstream from the pressure regulator, as described herein, the ink supply inlet pressure, typically 1-10 psi (28-277 inches of water), may be used to drive ink through the filter. The filter chamber, therefore, is a higher pressure chamber compared to the lower pressure regulator chamber. The much higher filter chamber pressure permits a much smaller filter to allow the desired flow to the printhead. 
     In the Edgeline Technology pens mentioned above, reconfiguring the pen as described herein reduces the desired filter area from 25 cm 2  to about 6.5 cm 2  and the total pen volume occupied by the pen through its full range of motion by up to 50% while still maintaining adequate ink flows. For an inlet pressure of 1-10 psi, a 6.5 cm 2  filter in a pen such as pen  40  described above has been shown to permit ink flows exceeding 100 cc/minute, a flow rate to filter area ratio of more than 15 (using the units of flow and area noted). By contrast, a conventional Edgeline Technology pen delivers a flow rate to filter area ratio of only about 3, permitting about 75 cc/minute ink flow through a 25 cm 2  filter. 
     The magnitude of the difference is readily apparent by comparing the filter frames illustrated in  FIGS. 8 and 9  and by comparing the ink pens illustrated in  FIGS. 3 and 10 . Referring first to  FIGS. 8 and 9 , filter frame  66 B is shown in  FIG. 8  and a corresponding conventional filter frame, designated part number 94, from an Edgeline Technology ink pen. The size of each filter frame  66 B and  94  is proportionate. Not only is the filter/flow area  96  in filter frame  66 B much smaller than the filter/flow area  98  in filter frame  94 , but the overall size of filter frame  66 B is but a small fraction of the overall size of the conventional filter frame  94 . The compounding affect of the filter frame size reduction is illustrated in pens  40  and  100  shown proportionately in  FIGS. 3 and 10 . Referring to  FIGS. 3 and 10 , a conventional Edgeline Technology ink pen  100  shown in  FIG. 10 , utilizing filter frames  94  from  FIG. 9 , is nearly twice the height of, and slightly longer than, an exemplary new ink pen  40  shown in  FIG. 3  utilizing the exemplary new filter frames  66 A and  66 B and the exemplary new flow configuration described above. While the ratio of ink flow rate to filter area will vary depending on the ink volume life of the pen, the pressure available to deliver ink to the pen, the size of the delivery tubes, the density of the filter media, and the cleanliness and viscosity of the ink, it is expected that an ink flow rate to filter area ratio of at least 15 may be achieved in many of the larger, higher performance inkjet pens like those used in the Hewlett-Packard Company Edgeline Technology printers. 
     As noted at the beginning of this Description, the exemplary embodiments shown in the figures and described above illustrate but do not limit the invention. Other forms, details, and embodiments may be made and implemented. Therefore, the foregoing description should not be construed to limit the scope of the invention, which is defined in the following claims.