Abstract:
A method of regulating pressure in an ink tank including biasing an aperture of the ink tank to a closed position, withdrawing ink from an outlet port of the ink tank to provide a reduced internal pressure in the ink tank. The aperture is opened in response to the reduced internal pressure in the ink tank. The aperture leads to ambient atmospheric pressure outside the ink tank. The biasing step can include using biasing a valve member with a predetermined force against a valve seat at a contact region between the valve member and the valve seat. Opening of the aperture can include moving the member away from the valve seat in response to a difference in pressure between ambient atmospheric pressure and the reduced internal pressure in the tank.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to commonly assigned U.S. patent application Ser. No. ______ filed concurrently herewith, entitled “Ink Tank Check Valve for Pressure Regulation”, the disclosure of which is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to an ink tank for an inkjet printer, and more particularly to a method for regulating the pressure in the ink tank. 
       BACKGROUND OF THE INVENTION 
       [0003]    An inkjet printer typically includes one or more printheads and their corresponding ink supplies. A printhead includes an array of drop ejectors, each ejector consisting of an ink pressurization chamber, an ejecting actuator and a nozzle through which droplets of ink are ejected. The ejecting actuator may be one of various types, including a heater that vaporizes some of the ink in the pressurization chamber in order to propel a droplet out of the nozzle, or a piezoelectric device which changes the wall geometry of the pressurization chamber in order to generate a pressure wave that ejects a droplet. The droplets are typically directed toward paper or other recording medium in order to produce an image according to image data that is converted into electronic firing pulses for the drop ejectors as the print medium is moved relative to the printhead. 
         [0004]    In some printers an ink reservoir can be located remotely from an intermediate ink supply that is co-located with the printhead. The remote reservoir can be connected to the intermediate ink supply, for example, by tubing in order to replenish the ink used by the printhead. Alternatively in other printers, an ink supply can be directly coupled to the printhead. For the case of ink supplies being mounted on the carriage of a carriage printer, the ink supply can be permanently mounted onto the printhead, so that the printhead needs to be replaced when the ink is depleted, or the ink supply can be detachably mounted onto the printhead, so that only the ink supply itself needs to be replaced when the ink is depleted. 
         [0005]    An ink supply should be capable of containing the ink without leakage during manufacture, storage, transportation, and the printing operation itself. The ink supply should be capable of containing the ink even under conditions where the pressure within the ink supply changes due to environmental conditions. Pressure variations can occur, for example, due to changes in ambient temperature or barometric pressure during storage or transportation. During the printing operation ink should be held at a suitably negative pressure relative to ambient so that ink does not drool out of the nozzles, and yet not at an excessively negative pressure that would lead to ink starvation and dropout during printing. Various designs for regulating pressure within an inkjet ink supply are known including spring-biased bags, capillary media, and bubble generators. 
         [0006]    It has been found that pigment particles in a pigmented ink can settle out in ink supply designs where ink is stored in a capillary media pressure regulator, partly due to the restriction of motion of pigment particles within the small passages of the capillary media, as described in more detail in commonly assigned US Published Patent Application 20090309940. Such settling of pigments particles, especially for larger pigment particles (e.g. larger than 30 nanometers), can result in defective images during the printing process. As a result, an ink supply using capillary media to store ink can lead to a limitation in pigment particle size that can be used. Such a limitation can be disadvantageous, because such larger particles can be beneficial for providing higher optical density in printed regions. 
         [0007]    In addition to compatibility with inks of interest, other evaluation metrics for ink supply and pressure regulation methods include extractable ink per volume of the supply and the amount of variation of pressure versus amount of ink extracted from the supply. What is needed is a method for regulating the pressure within an ink supply for a printhead that is capable of keeping the pressure substantially constant and within an acceptable range as ink is being used. For the case of ink supplies that are not replenished within the printer, the method should preferably facilitate the ink supply&#39;s ability to deliver a volume of ink that is a substantial fraction of the volume of the ink supply, in order to help keep the design of the printer compact. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is directed to overcoming one or more of the problems set forth above. Briefly summarized, according to one aspect of the invention, the invention resides a method of regulating pressure in an ink tank, including biasing an aperture of the ink tank to a closed position, withdrawing ink from an outlet port of the ink tank to provide a reduced internal pressure in the ink tank. The aperture is opened in response to the reduced internal pressure in the ink tank. The aperture leads to ambient atmospheric pressure outside the ink tank. The biasing step can include using biasing a valve member with a predetermined force against a valve seat at a contact region between the valve member and the valve seat. Opening of the apertures can include moving the member away from the valve seat in response to a difference in pressure between ambient atmospheric pressure and the reduced internal pressure in the tank. The difference in pressure that forces the member away from the valve seat is proportional to the predetermined force and inversely proportional to the area of the contact region. 
         [0009]    These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein: 
           [0011]      FIG. 1  is a schematic representation of an inkjet printer system; 
           [0012]      FIG. 2  is a perspective view of a portion of a printhead chassis; 
           [0013]      FIG. 3  is a perspective view of a portion of a carriage printer; 
           [0014]      FIG. 4  is a schematic side view of an exemplary paper path in a carriage printer; 
           [0015]      FIG. 5  is a cross sectional view of an ink tank according to an embodiment of the invention with the vent closed by a valve; 
           [0016]      FIG. 6  is a cross sectional view of an ink tank according to an embodiment of the invention with the vent opened by a valve; 
           [0017]      FIG. 7  is a graph of pressure at the outlet port of the ink tank versus time as ink is withdrawn at a constant rate; 
           [0018]      FIG. 8  is an enlarged cross sectional view of a portion of the valve of  FIG. 5 ; 
           [0019]      FIG. 9  is a portion of a carriage printer according to an embodiment of the invention; 
           [0020]      FIG. 10  is a cross sectional view of an ink tank according to an embodiment of the invention; 
           [0021]      FIG. 11  is a cross sectional view of an ink tank according to an embodiment of the invention; and 
           [0022]      FIG. 12  is a portion of a carriage printer with a remote ink supply connected to the ink tank of  FIG. 11  according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Referring to  FIG. 1 , a schematic representation of an inkjet printer system  10  is shown, for its usefulness with the present invention and is fully described in U.S. Pat. No. 7,350,902, and is incorporated by reference herein in its entirety. Inkjet printer system  10  includes an image data source  12 , which provides data signals that are interpreted by a controller  14  as being commands to eject drops. Controller  14  includes an image processing unit  15  for rendering images for printing, and outputs signals to an electrical pulse source  16  of electrical energy pulses that are inputted to an inkjet printhead  100 , which includes at least one inkjet printhead die  110 . 
         [0024]    In the example shown in  FIG. 1 , there are two nozzle arrays. Nozzles  121  in the first nozzle array  120  have a larger opening area than nozzles  131  in the second nozzle array  130 . In this example, each of the two nozzle arrays has two staggered rows of nozzles, each row having a nozzle density of 600 per inch. The effective nozzle density then in each array is 1200 per inch (i.e. d= 1/1200 inch in  FIG. 1 ). If pixels on the recording medium  20  were sequentially numbered along the paper advance direction, the nozzles from one row of an array would print the odd numbered pixels, while the nozzles from the other row of the array would print the even numbered pixels. 
         [0025]    In fluid communication with each nozzle array is a corresponding ink delivery pathway. Ink delivery pathway  122  is in fluid communication with the first nozzle array  120 , and ink delivery pathway  132  is in fluid communication with the second nozzle array  130 . Portions of ink delivery pathways  122  and  132  are shown in  FIG. 1  as openings through printhead die substrate  111 . One or more inkjet printhead die  110  will be included in inkjet printhead  100 , but for greater clarity only one inkjet printhead die  110  is shown in  FIG. 1 . The printhead die are arranged on a support member as discussed below relative to  FIG. 2 . In  FIG. 1 , first fluid source  18  supplies ink to first nozzle array  120  via ink delivery pathway  122 , and second fluid source  19  supplies ink to second nozzle array  130  via ink delivery pathway  132 . Although distinct fluid sources  18  and  19  are shown, in some applications it may be beneficial to have a single fluid source supplying ink to both the first nozzle array  120  and the second nozzle array  130  via ink delivery pathways  122  and  132  respectively. Also, in some embodiments, fewer than two or more than two nozzle arrays can be included on printhead die  110 . In some embodiments, all nozzles on inkjet printhead die  110  can be the same size, rather than having multiple sized nozzles on inkjet printhead die  110 . 
         [0026]    Not shown in  FIG. 1 , are the drop forming mechanisms associated with the nozzles. Drop forming mechanisms can be of a variety of types, some of which include a heating element to vaporize a portion of ink and thereby cause ejection of a droplet, or a piezoelectric transducer to constrict the volume of a fluid chamber and thereby cause ejection, or an actuator which is made to move (for example, by heating a bi-layer element) and thereby cause ejection. In any case, electrical pulses from electrical pulse source  16  are sent to the various drop ejectors according to the desired deposition pattern. In the example of  FIG. 1 , droplets  181  ejected from the first nozzle array  120  are larger than droplets  182  ejected from the second nozzle array  130 , due to the larger nozzle opening area. Typically other aspects of the drop forming mechanisms (not shown) associated respectively with nozzle arrays  120  and  130  are also sized differently in order to optimize the drop ejection process for the different sized drops. During operation, droplets of ink are deposited on a recording medium  20 . 
         [0027]      FIG. 2  shows a perspective view of a portion of a printhead chassis  250 , which is an example of an inkjet printhead  100 . Printhead chassis  250  includes three printhead die  251  (similar to printhead die  110  in  FIG. 1 ), each printhead die  251  containing two nozzle arrays  253 , so that printhead chassis  250  contains six nozzle arrays  253  altogether. The six nozzle arrays  253  in this example can each be connected to separate ink sources (not shown in  FIG. 2 ); such as cyan, magenta, yellow, text black, photo black, and a colorless protective printing fluid. Each of the six nozzle arrays  253  is disposed along nozzle array direction  254 , and the length of each nozzle array along the nozzle array direction  254  is typically on the order of 1 inch or less. Typical lengths of recording media are 6 inches for photographic prints (4 inches by 6 inches) or 11 inches for paper (8.5 by 11 inches). Thus, in order to print a full image, a number of swaths are successively printed while moving printhead chassis  250  across the recording medium  20 . Following the printing of a swath, the recording medium  20  is advanced along a media advance direction that is substantially parallel to nozzle array direction  254 . 
         [0028]    Also shown in  FIG. 2  is a flex circuit  257  to which the printhead die  251  are electrically interconnected, for example, by wire bonding or TAB bonding. The interconnections are covered by an encapsulant  256  to protect them. Flex circuit  257  bends around the side of printhead chassis  250  and connects to connector board  258 . When printhead chassis  250  is mounted into the carriage  200  (see  FIG. 3 ), connector board  258  is electrically connected to a connector (not shown) on the carriage  200 , so that electrical signals can be transmitted to the printhead die  251 . 
         [0029]      FIG. 3  shows a portion of a desktop carriage printer. Some of the parts of the printer have been hidden in the view shown in  FIG. 3  so that other parts can be more clearly seen. Printer chassis  300  has a print region  303  across which carriage  200  is moved back and forth in carriage scan direction  305  along the X axis, between the right side  306  and the left side  307  of printer chassis  300 , while drops are ejected from printhead die  251  (not shown in  FIG. 3 ) on printhead chassis  250  that is mounted on carriage  200 . Carriage motor  380  moves belt  384  to move carriage  200  along carriage guide rail  382 . An encoder sensor (not shown) is mounted on carriage  200  and indicates carriage location relative to an encoder fence  383 . 
         [0030]    Printhead chassis  250  is mounted in carriage  200 , and multi-chamber ink supply  262  and single-chamber ink supply  264  are mounted in the printhead chassis  250 . The mounting orientation of printhead chassis  250  is rotated relative to the view in  FIG. 2 , so that the printhead die  251  are located at the bottom side of printhead chassis  250 , the droplets of ink being ejected downward onto the recording medium in print region  303  in the view of  FIG. 3 . Multi-chamber ink supply  262 , in this example, contains five ink sources: cyan, magenta, yellow, photo black, and colorless protective fluid; while single-chamber ink supply  264  contains the ink source for text black. Paper or other recording medium (sometimes generically referred to as paper or media herein) is loaded along paper load entry direction  302  toward the front of printer chassis  308 . 
         [0031]    A variety of rollers are used to advance the medium through the printer as shown schematically in the side view of  FIG. 4 . In this example, a pick-up roller  320  moves the top piece or sheet  371  of a stack  370  of paper or other recording medium in the direction of arrow, paper load entry direction  302 . A turn roller  322  acts to move the paper around a C-shaped path (in cooperation with a curved rear wall surface) so that the paper continues to advance along media advance direction  304  from the rear  309  of the printer chassis (with reference also to  FIG. 3 ). The paper is then moved by feed roller  312  and idler roller(s)  323  to advance along the Y axis across print region  303 , and from there to a discharge roller  324  and star wheel(s)  325  so that printed paper exits along media advance direction  304 . Feed roller  312  includes a feed roller shaft along its axis, and feed roller gear  311  is mounted on the feed roller shaft. Feed roller  312  can include a separate roller mounted on the feed roller shaft, or can include a thin high friction coating on the feed roller shaft. A rotary encoder (not shown) can be coaxially mounted on the feed roller shaft in order to monitor the angular rotation of the feed roller. 
         [0032]    The motor that powers the paper advance rollers is not shown in  FIG. 3 , but the hole  310  at the right side of the printer chassis  306  is where the motor gear (not shown) protrudes through in order to engage feed roller gear  311 , as well as the gear for the discharge roller (not shown). For normal paper pick-up and feeding, it is desired that all rollers rotate in forward rotation direction  313 . Toward the left side of the printer chassis  307 , in the example of  FIG. 3 , is the maintenance station  330 . 
         [0033]    Toward the rear of the printer chassis  309 , in this example, is located the electronics board  390 , which includes cable connectors  392  for communicating via cables (not shown) to the printhead carriage  200  and from there to the printhead chassis  250 . Also on the electronics board are typically mounted motor controllers for the carriage motor  380  and for the paper advance motor, a processor and/or other control electronics (shown schematically as controller  14  and image processing unit  15  in  FIG. 1 ) for controlling the printing process, and an optional connector for a cable to a host computer. 
         [0034]      FIG. 5  shows a cross-sectional view of an ink tank  270  according to an embodiment of the invention. Ink tank  270  can be a chamber of multi-chamber ink supply  262  or single chamber ink supply  264  (see  FIG. 3 ). Ink tank  270  can be replaceably removable from printhead chassis  250  (see  FIGS. 2 and 3 ) or it can be permanently mounted on the printhead. Ink tank  270  includes a tank body  272  which contains a quantity of ink  274 . Above the ink  274  is an airspace  273 . Within the tank body  272  is an enclosure  275  that houses a valve  280 . Valve  280  (also sometimes referred to as a check valve herein) includes a closing member such as a ball  282 , and a valve seat  286 . Ball  282  is substantially spherical and can be made of a compliant material such as an elastomer. Similarly, valve seat  286  can include a compliant material. The compliancy of the closing member or the valve seat  286  can improve the quality of the seal of the valve when it is closed. A spring  284  biases the ball  282  against the valve seat  286  under normal operating conditions. An aperture serving as a vent  276  leading to ambient atmospheric pressure is also included in the tank body near one end of enclosure  275 . When check valve  280  is closed (i.e. when spring  284  pushes ball  282  into sealing contact against valve seat  286 ), air is not allowed to enter the tank body  272  through vent  276 . In other words, the valve is biased to close the vent. 
         [0035]    Ink tank  270  also includes an outlet port  279  which provides ink to the printhead (not shown in  FIG. 5 ), for example through a wick  271 . As ink  274  is extracted from ink tank  270  through outlet port  279  for printing or for printhead maintenance, the level of ink  274  in ink tank  270  decreases, as seen by comparing  FIG. 6  to  FIG. 5 . As a result, the volume of the airspace  273  increases. Since pressure of a quantity of air is inversely proportional to its volume, as the airspace  273  increases without adding more air (with vent  276  closed as in  FIG. 5 ), the pressure inside the ink tank  270  and at the outlet port  279  decreases relative to ambient pressure outside ink tank  270 . As ink  274  continues to be extracted from ink tank  270 , the pressure within the ink tank  270  becomes sufficiently reduced relative to ambient pressure that the bias force of spring  284  is overcome and the ball  282  of valve  280  moves away from valve seat  282  to open vent  276  as shown in  FIG. 6 . The incoming air enters enclosure  275  and can exit the enclosure  275  into the ink  274  through holes  277  in the end of the enclosure  275  that is in contact with the ink  274 . When sufficient air has entered the vent  276 , the spring  284  is again able to push ball  282  against valve seat  286  to close the vent  276 . 
         [0036]    The check valve  280  and vent  276  in this embodiment act as a pressure regulator for ink tank  270 . The rate of change of pressure P port  with time at outlet port  279  as ink  274  is extracted at an extraction rate Q port  prior to the opening of valve  280  to open vent  276  is calculated below. In this analysis, P is the pressure of the air in airspace  273 , P o  is the initial pressure of the air in airspace  273  before ink is extracted, ρ is the density of ink  274 , h is the height of the ink above the bottom of ink tank  270 , g is the acceleration due to gravity, V is the volume of the air in airspace  273 , V 0  is the volume of air in airspace  273  before ink is extracted, and A is the cross sectional area of ink tank  270 . 
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         [0037]    During extraction of ink  274  at a constant rate Q port  from outlet port  279  prior to the opening of valve  280 , the pressure in ink tank  270  decreases nearly linearly with time for typical tank configurations. This linear approach toward the designed operating pressure of about −5 inches of water relative to ambient pressure is shown as line  405  in  FIG. 7  where the ink extraction rate Q port  was 4 ml per minute. The valve  280  opens at point  410  in  FIG. 7 . Once the opening pressure of valve  280  is reached, air is allowed to flow into the ink tank  270 , preventing further lowering of the pressure. Since the regulated air entering ink tank  270  is doing so at a fixed height (near the bottom of tank  270 ), the pressure at the outlet port  279  does not continue to change with decreasing ink level, but instead, remains at a substantially constant regulated pressure equal to the valve opening pressure, as shown by line  420  in  FIG. 7 . 
         [0038]      FIG. 8  shows an enlarged cross-sectional view of ball  282  in contact with valve seat  286 . Valve seat  286  is conically shaped in this example and has an annular contact region  288  with ball  282 . Contact region  288  has an area A c . For an annular shaped contact region  288  having a width w and an average or midpoint radius R, the area A G  of contact region  288  is 2πRw. A compliant ball  282  and/or a compliant valve seat  286  will deform to an amount determined by the geometry, materials and load applied by spring  284 . The spring can be chosen with a spring constant and a compression displacement to provide a spring force F s  to bias ball  282  against valve seat  286  that is approximately related to the opening pressure of the valve by P open ˜F s /A c =F s /2πRw. The opening pressure P open  is the pressure difference between the ambient pressure and the reduced pressure within ink tank  270  that is sufficient to open check valve  280 , and is also substantially equal to the constant operating pressure illustrated in  FIG. 7  by line  420 . Frictional forces in valve  280 , as well as compression forces that deform the compliant ball  282  and/or valve seat  286  can cause P open  to deviate somewhat from F s /A c . 
         [0039]      FIG. 9  show an embodiment of the present invention including individual ink tanks  270  mounted on a printhead chassis  250  that is mounted on a carriage  200  of an inkjet printer, a portion of which is shown. Many of the part numbers of this example are similar to parts shown in  FIGS. 3 and 4  and will not be discussed further here. Each ink tank  270  includes a vent  276 . The valve and some other components of the ink tank  270  that are shown in  FIG. 5  are not shown in  FIG. 9 . In the embodiment shown in  FIG. 9 , a platform  334  including a finger  336  is mounted on rotational mount  338  above the maintenance station  330 . The rotational mount  338  allows the platform to be rotated out of the way for normal operation. Since the sense of rotation of rotational mount  338  is similar to the forward direction  313  (and its reverse) of feed roller  312 , rotation of the rotational mount  338  can be achieved by transmitting power from the paper advance motor (not shown) when needed. The purpose of finger  336  is to protrude into vent  276  and forcibly push down ball  282  (or other closing member) away from valve seat  286  of valve  280  (see  FIGS. 5 and 6 ) if the pressure becomes excessive within one or more of the ink tanks  270 . For example, if an ink tank  270  is partially depleted to the extent that the valve  280  has already opened to allow air to enter the tank through vent  276 , and subsequently the tank is exposed to a sufficiently elevated temperature, the pressure in the tank can become greater than ambient pressure. As a result, pressure at the outlet port  279  can become high enough that ink is forced out of the nozzles of the printhead. To avoid this occurrence, ink level in ink tank  270  and ambient temperature can be monitored. If the conditions of ink level below a predetermined level and temperature above a predetermined temperature are encountered, printer controller  14  can cause carriage  200  to move the tank below the position of finger  336 , and then rotate platform  336  to cause finger  336  to enter vent  276  and open valve  280  to relieve the excess pressure. Ink level can be monitored within the printer by knowing the initial fill level and tracking usage by counting ejected drops and multiplying by drop volume and counting maintenance operations and multiplying by volume of ink per maintenance operation. Temperature can be monitored within the printer by a temperature sensor that can be integrated into the printhead, or mounted on the printer electronics board  390 , for example. 
         [0040]    In the embodiments described above, the check valve  280  is used to regulate pressure in the ink tank  270  during usage of ink within the printer. In addition, check valve  280  keeps the pressure from reaching excessively negative levels even when ink is not being used—for example, during manufacture, storage or transportation when the ink tank  270  is not even installed in the printer.  FIG. 10  shows an embodiment where check valve  280  prevents pressure from reaching excessively negative levels when ink is not being used, but capillary member  278  is used to regulate pressure in the ink tank  270  when ink is being used in the printer. Capillary member  278  is disposed at an end of enclosure  275  that is in contact with ink  274 , i.e. opposite the end near which the vent  276  is located. In such an embodiment, pressure regulation is provided substantially as described in commonly assigned US Patent Application Publication 20090309940, incorporated herein in its entirety by reference. 
         [0041]    In the embodiments described above the aperture located in the tank body  272  near valve  280  has been a vent  276  to ambient atmospheric pressure. In the embodiments shown in  FIGS. 11 and 12 , the aperture is an inlet port  294 . A fitting  289  allows flexible tubing  292  to be connected to the ink tank  270  (see  FIG. 12 , where, for clarity, tubing  292  is shown leading only to one ink tank  270 ). Tubing  292  leads to a remote ink supply  290  (sometimes called an off-axis ink supply) stationarily mounted on the printer chassis  300 . When a sufficient amount of ink  274  is withdrawn from ink tank  270  for printing and/or maintenance, the pressure within the tank body  272  of ink tank  270  becomes reduced relative to the external ink pressure in the tubing  292  and remote ink supply  290 . At a predetermined pressure within the ink tank  270  relative to the external ink pressure, valve  280  is configured to open (see  FIG. 11 ), so that ink from the remote ink supply  290  can be replenished into ink tank  270 . The predetermined pressure is related to the spring force provided by spring  284  that biases valve  280  to a closed position. 
         [0042]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
       PARTS LIST 
       [0000]    
       
           10  Inkjet printer system 
           12  Image data source 
           14  Controller 
           15  Image processing unit 
           16  Electrical pulse source 
           18  First fluid source 
           19  Second fluid source 
           20  Recording medium 
           100  Inkjet printhead 
           110  Inkjet printhead die 
           111  Substrate 
           120  First nozzle array 
           121  Nozzle(s) 
           122  Ink delivery pathway (for first nozzle array) 
           130  Second nozzle array 
           131  Nozzle(s) 
           132  Ink delivery pathway (for second nozzle array) 
           181  Droplet(s) (ejected from first nozzle array) 
           182  Droplet(s) (ejected from second nozzle array) 
           200  Carriage 
           250  Printhead chassis 
           251  Printhead die 
           253  Nozzle array 
           254  Nozzle array direction 
           256  Encapsulant 
           257  Flex circuit 
           258  Connector board 
           262  Multi-chamber ink supply 
           264  Single-chamber ink supply 
           270  Ink tank 
           271  Wick 
           272  Tank body 
           273  Airspace 
           274  Ink 
           275  Enclosure 
           276  Vent 
           277  Hole 
           278  Capillary member 
           279  Outlet port 
           280  Valve 
           282  Ball 
           284  Spring 
           286  Valve seat 
           288  Contact region 
           289  Fitting 
           290  Remote ink supply 
           292  Tubing 
           294  Inlet port 
           300  Printer chassis 
           302  Paper load entry direction 
           303  Print region 
           304  Media advance direction 
           305  Carriage scan direction 
           306  Right side of printer chassis 
           307  Left side of printer chassis 
           308  Front of printer chassis 
           309  Rear of printer chassis 
           310  Hole (for paper advance motor drive gear) 
           311  Feed roller gear 
           312  Feed roller 
           313  Forward rotation direction (of feed roller) 
           320  Pick-up roller 
           322  Turn roller 
           323  Idler roller 
           324  Discharge roller 
           325  Star wheel(s) 
           330  Maintenance station 
           332  Cap 
           334  Platform 
           336  Finger 
           338  Rotational mount 
           370  Stack of media 
           371  Top piece of medium 
           380  Carriage motor 
           382  Carriage guide rail 
           383  Encoder fence 
           384  Belt 
           390  Printer electronics board 
           392  Cable connectors 
           405  Line (pressure vs time before valve opens) 
           410  Point (time at which valve opens) 
           420  Line (pressure vs time after valve opens)