Abstract:
A print head reservoir includes a plate having first and second sides and a passage extending through said plate. The plate defines an angled channel in communication with the passage and an outlet region.

Description:
BACKGROUND  
       [0001]     Ink jet printers create an image on a surface by ejecting ink through orifices in a print head face plate onto a substrate. The print head face plate communicates with a print head reservoir, which communicates with an ink source. Solid ink printers melt solid ink and deliver the melted ink to the print head reservoir.  
         [0002]     When the solid ink printer is turned off, the ink that remains in the print head reservoir can freeze. When the ink thaws in the print head reservoir, air that was once in solution in the ink can come out of solution to form air-bubbles or air pockets in the print head reservoir. Air pockets can impede the filtering of the ink as it travels toward the orifices in the print head face plate. Air pockets can also impair the print quality of the printer when an air bubble, as opposed to ink, is delivered through the orifice resulting in an unintended blank spot on the print media. Accordingly, it is desirable to purge periodically the cavities and channels in the print head reservoir to increase print quality.  
         [0003]     It is known to purge air out of solid ink print heads using a vacuum system, but a vacuum system is costly, time consuming and less efficient than a system that uses positive pressure. Furthermore, it is desirable to wipe the jets during purging, which is not possible when using a vacuum system. Accordingly, a positive pressure purge system is desirable. In a positive pressure purge system it is desirable to purge the print head using as little ink as possible.  
       BRIEF DESCRIPTION  
       [0004]     A print head reservoir for a printer includes a plate having first and second sides and a passage extending through the plate. The plate defines an angled channel in communication with the passage and an outlet region located near an intersection of at least two adjacent sloping portions of the angled channel.  
         [0005]     A print head reservoir for a printer includes a plate having a first surface and a second surface. The first surface defines a first channel and a second channel. The second surface defines a first ink cavity and a second ink cavity laterally spaced along the plate from the first ink cavity. The first ink cavity communicates with the first channel and the second ink cavity communicates with the second channel.  
         [0006]     A print head reservoir for a printer includes an ink source and a plate. The plate includes a channel formed on a first surface, a passage extending through the plate and in communication with the channel and the ink source, and first and second outlet regions defined in the plate each in communication with the channel. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a front perspective view of a print head reservoir for an ink jet printer.  
         [0008]      FIG. 2  is a front perspective view of a rear plate of the print head reservoir of  FIG. 1 .  
         [0009]      FIG. 3  is a view of a side cross-section of the print head reservoir of  FIG. 1 .  
         [0010]      FIG. 4  is a rear perspective view of a middle plate of the print head reservoir of  FIG. 1 .  
         [0011]      FIG. 5  is a close up view of an inlet of the middle plate of  FIG. 4 .  
         [0012]      FIG. 6  is an elevation view of the front side of the middle plate of  FIG. 4 .  
         [0013]      FIG. 7  is a close up cross section of the upper portion of the print head reservoir of  FIG. 1 .  
         [0014]      FIG. 8  is an elevation view of the rear side of a front plate of the print head reservoir of  FIG. 1 .  
         [0015]      FIG. 9  is an elevation view of the front side of the front plate of  FIG. 8 .  
         [0016]      FIG. 10  is a front elevation view of the print head reservoir of  FIG. 1  including a fourth plate attached to the front side of the front plate.  
         [0017]      FIG. 11  is a perspective view of an ink jet printer that contains the print head reservoir of  FIG. 1 .  
         [0018]      FIG. 12  is a cross-sectional view of the ink jet printer of  FIG. 11 .  
     
    
     DETAILED DESCRIPTION  
       [0019]     Referring to  FIGS. 11 and 12 , a print head A for an ink jet printer B generally delivers liquid ink to a jet stack C that transfers the ink onto a drum D. The print media, which can include paper, travels around the drum and picks up the ink deposited on the drum. Air can get into the pathway of the ink as it travels through the print head. To remove the air from the pathway, the print head reservoir is purged, which will be described in more detail below.  
         [0020]     With reference to  FIG. 1 , a print head reservoir  10  includes a first or front plate  12 , a second or middle plate  14  and a third or rear plate  16 . The print head reservoir  10  is a portion of the print head and is situated inside the ink jet printer such that the bottom of each plate is substantially horizontal and the reservoir can rotate about a pair of journals  18  (only one visible in  FIG. 1 ). The terms “front,” “middle,” and “rear” are used for ease of understanding to describe the components of the reservoir as they are shown in the figures; the terms are not used to limit the position of components in relation to one another.  
         [0021]     Generally, the ink travels from the rear plate  16  towards the front plate  12 . With reference to  FIG. 2 , the rear plate includes a front side  20  that is adjacent the middle plate  14  when the reservoir is assembled and a rear side  22  opposite the front side. A plurality of bucket walls  24  extend from the rear side  22  to define a plurality of ink buckets  26 . In the embodiment depicted, four ink buckets are shown and each bucket receives a different color ink, particularly yellow, cyan, magenta and black; however, a fewer or greater number of ink buckets can be provided and the ink buckets can receive different colors of ink. The ink buckets  26  usually receive ink that has been melted and dripped into the buckets; however, liquid ink that has not been melted can also be delivered to the ink buckets.  
         [0022]     With reference to  FIG. 3 , each ink bucket  26  communicates with a passage  28  which communicates with a rear plate outlet  32 . A filter  34  is disposed in each ink bucket on a shoulder  36  that projects inwardly from the bucket wall  24  into the ink bucket  26 . The filter  34  removes any impurities in the ink before the ink travels into the passage  28  and towards the rear plate outlet  32 . The rear plate outlet  32  communicates with a middle plate inlet  40  through a valve member  42 . The valve member  42  comprises a component of a one-way check valve that allows ink to pass from the rear plate outlet  32  into the middle plate inlet  40 . The valve member  42  precludes ink from passing from the middle plate inlet  40  back into the rear plate outlet  32 . The valve member  42  opens and closes in response to a pressure differential between the rear plate outlet  32  and the middle plate inlet  40 .  
         [0023]     Referring to  FIG. 4 , the middle plate  14  includes a front side  44  and a rear side  46 . The front side  44  of the middle plate abuts the front plate  12  and the rear side  46  of the middle plate abuts the front side  20  of the rear plate  16 . The middle plate inlet  40  includes three lobes situated 120 degrees apart from one another formed in the rear side  46  of the middle plate  16 . Two lobes  52  depend generally downward and the third lobe  50  extends upward to communicate with an ink chamber  56 . Each downward depending lobe  52  includes an opening  58  that communicates with a passage  64  (only one shown in phantom in  FIG. 3 ) which communicates with a middle plate outlet  68  on the front side  44  of the middle plate  14 . As seen in  FIG. 6 , eight middle plate outlets  68  are provided at the bottom of the front side  44  of the middle plate, two for each color of ink. A greater or fewer number of middle plate outlets can be provided.  
         [0024]     With reference back to  FIG. 4 , ink flows into the middle plate inlet  40  and into the ink chamber  56  through the upward lobe  50 . Ink exits the ink chamber through openings  58  ( FIG. 5 ) in the downward lobes  52 . The ink chamber  56  is defined as a depression in both the rear side  46  of the middle plate  14  and the front side  20  of the rear plate  16 , as seen in  FIG. 3 . Ink exits the middle plate outlets  68 , which are in communication with the passages  64  (only one shown), and enters an upstream filter cavity  74 .  
         [0025]     A vertical filter  76  is sandwiched between and situated substantially parallel to the front plate  12  and the middle plate  14 . The upstream filter cavity  74  is defined between the front side  44  of the middle plate  14  and the filter  76 . As more clearly seen in  FIG. 7 , the filter  76  includes two layers, a first layer  78  made of a fine screen and a second layer  82  made of a felt material. Each of the filters can remove impurities as small as  10  microns from the ink. Ink flows through the filter  76  from the upstream filter cavity  74  into a downstream filter cavity  86 , which will be described in more detail below.  
         [0026]     The front plate  12  includes a front side  90  ( FIG. 9 ) and a rear side  92  ( FIG. 8 ), which is adjacent the filter  76 . The downstream filter cavity  86  is defined between the filter  76  and the rear side  92  of the front plate  12 . Referring to  FIG. 8 , the front plate  12  includes a plurality of openings  94  on the rear side  92  that communicate through passages with a plurality of front plate outlets  96  ( FIG. 9 ) on the front side  90  of the front plate. For ease of understanding the figures only, not as limiting the embodiment, the openings and front plate outlets will be described as having a certain color ink flowing through them.  
         [0027]     The rear side  92  of the front plate  12  includes four depressions that define four downstream filter cavities  86 . The downstream cavities will be referred to as  86 B,  86 M,  86 C and  86 Y, where the letter refers to the color of ink (black, magenta, cyan and yellow) in the downstream cavity. As can be seen in  FIG. 8 , some downstream filter cavities have more than one opening  94 , thus on the front side  90  of the front plate  12  more than one plate outlet  96  can be provided for a particular color. For example, the black downstream filter cavity  86 B has one opening  94 B, the magenta downstream filter cavity  86 M has three openings  94 M, the cyan downstream filter cavity  86 C has two openings  94 C and the yellow downstream filter cavity  86 Y has one opening  94 Y. Each of these openings  94  communicates with a corresponding front plate outlet  96  ( FIG. 9 ) through a passage.  
         [0028]     With reference to  FIG. 9 , the front side  90  of the front plate  12  includes a plurality of angled channels  98  formed in the plate. Each front plate outlet  96  is disposed in an angled channel. The channels  98  deliver ink laterally across the front plate  12  to a plurality of corresponding outlet regions  102 , where the ink can pass through a fourth plate  100  ( FIG. 10 ) en route to the jet stack (not shown). In the embodiment depicted, each color has four outlet regions  102  equally spaced laterally along the front plate. For ease of explanation of the embodiment disclosed, and not to be deemed as limiting, the channels and the outlet regions will be referred to with a suffix following the reference numeral that corresponds to the color of ink that travels through the channel toward the outlet region.  
         [0029]     As seen in  FIG. 9 , channel  98 Y receives yellow ink from front plate outlet  96 Y and delivers the yellow ink to four outlet regions  102 Y evenly spaced laterally along and near the top of the front side  90  of the front plate  12 . Channel  98 B receives black ink from front plate outlet  96 B and delivers black ink to four outlet regions  102 B situated next to the yellow outlet regions  102 Y. To deliver black ink to three of the outlet regions  102 B would require the black ink channel  98 B to cross over the yellow ink channel. To route the black ink to the outlet regions  102 B without crossing over the yellow ink channel  98 Y, channel openings  104 B are provided at the apex of angled portions of the black channel  98 B. The channel openings  104 B communicate through a passage to corresponding underpass inlets  106 B in the rear side  92  of the front panel  12  ( FIG. 8 ). The underpass inlets  106 B communicate with corresponding underpass channels  108 B formed on the rear side  92 . The underpass channels lead to underpass outlets  112 B which communicate through a passage with a corresponding outlet region  102 B on the front side  90  of the front plate  12  ( FIG. 9 ). This is also shown in cross-section in  FIG. 7 . As shown in FIGS.  6 ,  7 and  8  the underpass channels  108 B are formed as depressions in both the rear side  92  of the front plate  12  and the front side  44  of the middle plate  14 .  
         [0030]     Referring back to  FIG. 9 , two separate channels  98 C are provided to carry cyan ink towards four outlet regions  102 C evenly spaced laterally along and near the bottom of the front plate  12 . As depicted in  FIG. 9 , the left most first plate outlet  96 C communicates with the left channel  98 C to deliver cyan ink to the two left outlet regions  102 C. The left channel also includes a channel opening  104 C, similar to the channel opening described above. The channel opening  104 C communicates through a passage to a corresponding underpass inlet  106 C ( FIG. 8 ) in the rear side  92  of the front panel  12 . The underpass inlet  106 C communicates with a corresponding underpass channel  108 C formed on the rear side  92 . The underpass channel  108 C leads to an underpass outlet  112 C which communicates through a passage with a corresponding left most outlet region  102 C (as shown in  FIG. 9 ) on the front side  90  of the front plate  12 . With reference to  FIG. 6 , the cyan underpass channel  108 C is also defined on the front side  44  of the middle plate  14 . Three channels  98 M in communication with three magenta front plate outlets  96 M carry magenta ink towards four outlet regions  102 M. Each magenta outlet region  102 M is situated next to a corresponding cyan outlet region  102 C.  
         [0031]     As mentioned earlier, melted ink travels through the printer reservoir  10 . When the printer is turned off, the ink can freeze in the printer reservoir. During the freeze process, air comes out of solution that was previously dissolved in the liquid ink. When the printer is turned back on and the printer reservoir is warmed up, the air that has come out of solution is left as bubbles in the liquid ink.  
         [0032]     One area of the printer reservoir  10  where the air bubbles can form is in the channels  98  on the front side  92  of the first plate  12 . The channels are angled or sloped towards the outlet regions  102  to encourage the air bubbles to passively move toward the outlet regions through buoyancy of the air bubble. As seen in  FIG. 9 , the outlet regions  102  are located at the apex of angled portions of the channels  98 . With the air bubbles moved towards the outlet regions  102 , purging the air bubbles out of the channels  98  requires a minimal amount of ink. Purging the channel is, generally, passing enough ink through the channel  98  to expel any air bubbles that have formed in the channel. The ink can be passed through the channels at a greater pressure during a purge cycle by, for example, forcing air into the ink chambers  56  by way of an air pressure source, which is in communication with the channels  98 . The particular angle or slope of the channel is determined such that large bubbles generate enough unconstrained buoyancy to overcome the surface tension holding them in position.  
         [0033]     The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occurto others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.