Patent Publication Number: US-8113627-B2

Title: Micro-fluidic actuator for inkjet printers

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is filed concurrently with and has related subject matter to U.S. patent application Ser. No. 12/487,675, filed Jun. 19, 2009 titled “Inkjet Printers Having Micro-Fluidic Actuators”, with Yonglin Xie as the inventor. 
     FIELD OF THE INVENTION 
     The present invention generally relates to inkjet printing devices and more particularly to such inkjet printing devices having a micro-fluidic actuator with a flexible membrane that displaces ink from its ink reservoir according to the displacement of the flexible membrane. 
     BACKGROUND OF THE INVENTION 
     Currently, there are various mechanisms for ejecting ink from an ink reservoir. For example, US Patent Publication 2006/0232631 A1 discloses an ink reservoir having a piston in the ink reservoir which is movable to cause ink to be ejected from the reservoir. The piston is connected to a heating element that is energized that causes the heating element to expand which, in turn, causes the piston to move to eject the ink. Although pistons are satisfactory, improvements are always desirable. For example, heating elements usually require a high input voltage which is not desirable. 
     While not an ink ejecting system, U.S. Pat. No. 6,811,133 B2 discloses a hydraulic system having a primary movable membrane with a piezoelectric material and a secondary movable membrane. Fluid is disposed between the primary and secondary membrane, and the piezoelectric material of the primary membrane is energized for causing the primary membrane to bow which, in turn, causes the secondary membrane to bow. The bowing of the secondary membrane functions as a valve in which the valve is opened and closed according to movement of the secondary membrane. Consequently, valve structures of this type are not needed for inkjet printing devices to eject ink. 
     Existing thermal inkjet actuators (bubble jet) boils ink directly to produce vapor bubbles to eject liquid drops. Such devices have limited ink latitude (aqueous based inks only) and suffer from reliability problems related to kogation (solid deposits baked onto the surface of the heater surface) and heater failure due to repeated heating to high temperatures. Existing non-thermal inkjet actuators (piezo-actuator or electrostatic actuator) have much wider ink latitude (aqueous and non-aqueous based inks) as well as longer lifetime. However, such actuators have small (sub-micron) displacement; therefore, a large actuator area is needed to displace sufficient amount of liquid to produce desired drop volume. As a result, it is very difficult to achieve high nozzle density required for high-resolution printing. Also, high voltage or high current are needed to activate such inkjet actuators, which require expensive and complicated drive electronics and limit maximum operating frequency. 
     Consequently, a need exists for a non-thermal ink ejecting mechanism in which large actuator displacement can be achieved with low input voltage or energy. 
     SUMMARY OF THE INVENTION 
     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 in a micro-fluidic actuator comprising an inlet channel through which fluid enters; a chamber through which the fluid is received from the inlet channel; an outlet channel that receives the fluid from the chamber and passes the fluid through the outlet channel so that a conduit pathway for the fluid is formed from the inlet channel, chamber and outlet channel; a flexible member that forms a portion of a wall of the chamber and that displaces in response to fluidic pressure in the chamber; and at least a first valve in the conduit pathway which, when the valve is activated, causes flow of the fluid through the conduit pathway to be altered so that pressure of the fluid passing through the chamber changes which, in turn, causes the flexible member to displace. 
     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 
       While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the present invention, it is believed that the invention will be better understood from the following description when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1A  is a side, cross-sectional view of the micro-fluidic actuator of the present invention having a pressure chamber for displacing a flexible membrane; 
         FIG. 1B  illustrates  FIG. 1A  in which the inlet valve is partially closed and the flexible membrane is partially retracted inwardly; 
         FIG. 1C  illustrates  FIG. 1A  in which the inlet valve is fully closed and the flexible membrane is retracted to its maximum capacity inwardly; 
         FIG. 1D  illustrates  FIG. 1A  in which the outlet valve is partially closed and the flexible membrane is partially expanded outwardly; 
         FIG. 1E  illustrates  FIG. 1A  in which the outlet valve is fully closed and the flexible membrane is expanded to its maximum capacity outwardly; 
         FIG. 2  illustrates  FIG. 1A  in which the flexible membrane is corrugated; 
         FIG. 3A  is an alternative embodiment of the micro-fluidic actuator of the present invention; 
         FIG. 3B  illustrates  FIG. 3A  in which the outlet valve is partially closed and the flexible membrane is partially expanded outwardly; 
         FIG. 3C  illustrates  FIG. 3A  in which the outlet valve is fully closed and the flexible membrane is extended outwardly to its maximum capacity; 
         FIG. 3D  is a third embodiment of the micro-fluidic actuator of the present invention; 
         FIG. 3E  illustrates  FIG. 3D  in which the inlet valve is partially closed and the flexible membrane is partially retracted inwardly; 
         FIG. 3F  illustrates  FIG. 1A  in which the inlet valve is fully closed and the flexible membrane is retracted inwardly to its maximum capacity; 
         FIG. 4A  illustrates the micro-fluidic actuator of  FIG. 1A  having an inkjet reservoir; 
         FIG. 4B  illustrates  FIG. 4A  in which ink is retracted into the ink reservoir; 
         FIG. 4C  illustrates  FIG. 4A  in which ink is ejected from the ink reservoir; 
         FIG. 5  is a printhead chassis of an inkjet printer of the present invention; 
         FIG. 6  is a perspective view of a portion of a desktop carriage printer of the present invention; and 
         FIG. 7  is a simplified block diagram of the paper flow system of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1A , there is shown a side view in cross-section of the micro-fluidic actuator  102  of the present invention. It is noted that, in the drawings, the flow of fluid in the drawings is indicated by the enlarged arrow. The micro-fluidic actuator  102  includes a solid, box-shaped base member  104 , preferably made of silicon, having a cut-away, upper portion that forms a pressure chamber  106 . Fluid enters an inlet channel  108 , passes into the chamber  106  and exits through an outlet channel  110 . It is noted that a pressure source (not shown) provides a positive pressure +P on fluid at the inlet channel  108  and a vacuum source (not shown) provides a negative pressure −P′ on fluid at the outlet channel  110 , both of which apply the needed pressure and vacuum to the fluid to cause the fluid to circulate therethrough. The magnitudes of P and P′ can be chosen to be the same, or they can be chosen to be different. The fluid is preferably either water, or a low boiling point fluid such as ethanol, methanol, or 3M Fluorinert® liquid. 
     The actuator  102  includes side walls  112  having a first side portion  114 , preferably made of silicon, and a second side portion  116 , preferably made of oxide or a polymer, joined together. Together the first and second portions  114  and  116  completely surround the base member  104  so that the fluid is contained therein. A top-enclosure  118  forms a covering of the actuator  102  and includes an inflexible member  120 , preferably made of a dielectric, disposed on the outer portion of the actuator  102  and attached to the side walls  112 . The top enclosure  118  includes a flexible member (referred to herein interchangeably as a membrane), preferably made of a dielectric, which spans and covers the chamber  106  and forms a top wall for the chamber  106 . For clarity of understanding, it is noted that a conduit pathway for the fluid is formed from the inlet channel  108 , chamber  106  and outlet channel  110 . 
     It is noted that the flexible membrane  122  may be made of a number of different materials. For example, the flexible membrane  122  may be a dielectric such as silicon nitride, silicon oxide or silicon carbide. The flexible membrane may also be a polymer such as polymide. The flexible membrane  122  may also be a silicon, metal, or metal alloy. The above list is a representative list of materials and is not intended to limit the scope of the invention. 
     Two MEMS (micro-electro-mechanical system) valves  124   a  and  b  are disposed respectively in the inlet channel  108  and outlet channel  110  and are preferably made of a metal bi-morph (i.e. a thermal actuator valve) or a piezoelectric material. The valves  124   a  and  124   b  may also be made of metal tri-morph, an electrostatic actuator or a heater that boils the liquid to form a vapor bubble to modulate the flow passing through the inlet channel  108  or the outlet channel  110  where the particular valve  124   a  or  124   b  is located. The valve  124   a  in the inlet channel  108  will be called an inlet valve  124   a  and the valve  124   b  in the outlet channel  110  will be called an outlet valve  124   b . Both valves  124   a  and  124   b  are actuated by any suitable means (not shown) suitable to operate the valves such as a voltage supply or the like. Fluid enters the inlet channel  108 , and when both valves  124   a  and  124   b  are open (not actuated), fluid flows freely through the chamber  106  and out of the outlet channel  110 . In this mode, the chamber pressure P 1  is substantially equal to zero, so that the flexible membrane  122  is not displaced. 
     Referring to  FIG. 1B , the fluid enters the inlet channel  108 , and when the inlet valve  124   a  is partially actuated so that flow of the fluid through the inlet channel  108  is partially obstructed and the outlet valve  124   b  is not actuated (the outlet channel is unobstructed), the chamber pressure P 1  decreases so that the membrane  122  is displaced inwardly toward the interior of the chamber  106 . The chamber pressure P 1  in  FIG. 1B  is less than zero, but less negative than −P which causes the flexible member  122  to displace inwardly. Referring to  FIG. 1C , when the inlet valve  124   a  is fully actuated to completely obstruct or stop the flow of the fluid through the fluid the inlet channel  108  and the outlet valve  124   b  is not actuated (the outlet channel is unobstructed), the pressure in the chamber  106  decreases further to be approximately equal to −P′, so that the flexible member  122  is displaced inwardly to an even greater extent (i.e., maximum capacity) than when the flow is partially obstructed. 
     Referring to  FIG. 1D , when the outlet valve  124   b  is partially actuated to partially obstruct the flow of the fluid through the outlet channel  110  and the inlet valve  124   a  is not actuated, the pressure P 1  in the chamber increases to greater than zero, but less than +P, so that the membrane  122  is displaced outwardly from the interior of the chamber  106 . The fluid enters through the inlet chamber  108 , passes into the chamber  106 , increases pressure P 1  in the chamber  106  due to the partially obstructed outlet channel  110  (thereby displacing the membrane  122 ) and exits through the outlet channel  110 . As noted in  FIG. 1E , when the outlet valve  124   b  is fully actuated to completely obstruct the flow of the fluid through the outlet channel  110  and the inlet valve  124   a  is open, the pressure in the chamber  106  increases to approximately +P, so that the flexible member  122  is displaced outwardly from the interior of the chamber  106  to an even greater extent (i.e., maximum capacity) than when the outlet channel  110  is partially obstructed as in  FIG. 1D . 
     For a given pressure P 1  in the chamber  106 , the amount of membrane displacement also depends on other factors such as the membrane physical properties and dimensions. All things equal, a membrane  122  with lower elastic modulus produces larger displacement. All things equal, a membrane  122  with less thickness, such as less than 10 microns, produces larger displacement. In addition, membrane thickness that is small compared to the lateral dimensions of the membrane is better for larger displacement. For example, a membrane thickness that is less than ⅕ of the minimum width of the membrane is better for larger displacement. All things equal, a membrane  122  with larger area produces larger displacement provided the aspect ratio of the membrane  122  is the same. 
     As will be discussed in detail hereinbelow, displacement of the membrane  122  inwardly and outwardly is beneficial when used in printing devices such as inkjet printing devices to eject ink. Although an inkjet printing device is used as an illustrative embodiment, the micro-fluidic actuator  102  of the present invention may be used on any suitable printing device or fluid handling device. 
     Referring to  FIG. 2 , there is shown an alternative embodiment of the present invention. The micro-fluidic actuator  102  includes a corrugated, flexible membrane  122  which permits higher displacement of the membrane  122  than the embodiment of  FIGS. 1A-1E . By being corrugated, the flexible membrane  122  is inherently longer than the opening over the chamber  106  over which it spans and covers. This permits the membrane  122  to have greater displacement. For thoroughness, it is noted that the operation of the valves  124   a  and  124   b  displaces the membrane  122  the same as described in  FIGS. 1A-1E . 
     Referring to  FIGS. 3A-3C , there is shown another alternative embodiment of the present invention. In this embodiment, a portion of the side wall  112  includes a protruding portion  126  which forms a portion of the chamber  106 , and the base member  104  includes a protruding portion  128  which forms the other portion of the chamber  106 . The flexible membrane  122  extends spanning the chamber  106  and the inlet channel  108  is disposed between the protruding portion  128  of the base member  104  and the protruding portion  126  of the side walls  126 . A MEMS outlet valve  124   b  is positioned in the outlet channel  110  on the base member  104 , and the outlet channel  110  is disposed between the base member  104  and the opposite side wall  112 . Fluid enters the inlet channel  108  and into the pressure chamber  106 , and when the outlet valve  124   b  is not actuated, the pressure P 1  in the pressure chamber  106  is approximately equal to zero, so that the flexible membrane  122  is not displaced but is in a non-flexed position or state. The fluid then exits the outlet channel  110 . Referring to  FIG. 3B , however, when the outlet valve  124   b  is partially actuated to partially obstruct the flow of the fluid through the outlet channel  110 , the pressure P 1  in the pressure chamber  106  is greater than 0 but less than +P, so that the flexible membrane  122  is displaced outwardly away from the interior of the chamber  106 . Referring to  FIG. 3C , when the outlet valve  124   b  is completely closed to completely stop or obstruct the flow of the fluid through the outlet channel  110 , the pressure P 1  in the pressure chamber increases further to approximately +P, so that the flexible member  122  is displaced outwardly from the interior of the pressure chamber  106  to an even greater extent (i.e., maximum capacity) than when the outlet valve  124   b  is partially closed. 
     Referring to  FIGS. 3D-3F , there is shown yet another alternative embodiment of the present invention. In this embodiment, a portion of an opposite side wall  112  includes a protruding portion  126  which forms a portion of the chamber  106 , and an opposite portion of the base member  104  includes a protruding portion  128  which forms the other portion of the chamber  106 . The flexible membrane  122  extends spanning the chamber  106  and the outlet channel  110  is disposed between the protruding portion  128  of the base member  104  and the protruding portion  126  of the side wall  112 . An inlet valve  124   a  is positioned in the inlet channel on the base member, and the inlet channel  108  is disposed between the base member  104  and the side wall  112  and across the inlet valve  124   a . Fluid passes into the inlet channel  108 , passes through the pressure chamber  106  and exits the outlet channel  110 . When the inlet valve  124   a  is not actuated, the fluid flows unobstructed and the pressure P 1  in the pressure chamber  106  is approximately equal to zero. The flexible membrane  122  is not displaced but is in a non-flexed position or state. Referring to  FIG. 3E , when the inlet valve  124   a  is partially actuated to partially obstruct the flow of the fluid through the inlet channel  108 , the pressure P 1  in the pressure chamber  106  is less than zero, but is greater than −P′, so that the flexible membrane  122  is displaced inwardly toward the interior of the pressure chamber  106 . Referring to  FIG. 3F , when the inlet valve  124   a  is fully actuated to completely obstruct the flow of the fluid through the inlet channel  108 , the chamber pressure  106  becomes approximately −P′, so that the flexible membrane  122  is displaced to an even greater extent (i.e, maximum capacity) than when the inlet channel  108  is partially obstructed. 
     Referring to  FIG. 4A , the embodiment of  FIG. 1A  is shown in an inkjet environment in which all the components of  FIG. 1A  are shown integrated with an inkjet reservoir  130  and a nozzle  132 . The flexible member  122  is located on a portion of a shared wall between the chamber and the reservoir. The micro-fluidic actuator  102  integrated with its inkjet reservoir  130  and a nozzle  132  is hereinafter referred to as a micro-fluidic drop ejector  134 . The reservoir  130  includes ink  136 , which is either ejected from the reservoir  130 , not ejected from the reservoir  130  or further retracted into the reservoir  130  according to the pressure applied by the flexible member  122 . As shown in  FIG. 4A , with both the inlet valve  124   a  and the outlet valve  124   b  open, the pressure P 1  in the pressure chamber  106  is approximately equal to zero so that the flexible membrane  122  is not displaced (as described relative to  FIG. 1A ) but is in its normal, non-flexed position and ink  136  is not ejected from the reservoir  130 . Referring to  FIG. 4B , when the inlet valve  124   a  is fully closed and the outlet valve  125   b  is open so that the pressure P 1  in the pressure chamber  106  is approximately equal to −P′ and the flexible membrane  122  is displaced inwardly toward the interior of the pressure chamber  106  (as described relative to  FIG. 1C ), ink  136  is retracted back into the ink reservoir  130 . Referring to  FIG. 4C , when the outlet valve  124   b  is fully closed and the inlet valve  124   a  is open so that the pressure P 1  in the pressure chamber  106  is approximately equal to +P and the flexible membrane  122  is displaced outwardly (as described in  FIG. 1E ), an ink droplet  138  is ejected from the ink reservoir  130 . 
     The above paragraph describes the inkjet environment relative to the embodiment of  FIGS. 1A-1E  with the membrane positions of  FIGS. 1A ,  1 C and  1 E; however, it is understood that each of the embodiments of  FIGS. 1A  though  3 F work similarly with the ink reservoir  130 . When the flexible membrane  122  is displaced inwardly toward the interior of the pressure chamber  106 , ink  136  is retracted into the ink reservoir  130 . When the flexible membrane  122  is in its normal, non-displaced state, the ink  136  is not displaced in either direction and the ink level is unchanged. The more the displacement of the flexible membrane  122  outwardly from the reservoir  130 ; the more the ink  136  protrudes from the nozzle  132 . When the membrane  122  is sufficiently displaced outwardly, a droplet of ink  128  breaks off and is ejected from the ink reservoir  130 . As should be apparent to those skilled in the art, ink  136  is ejected from the reservoir  130  according to the displacement of the flexible membrane  122 —the more the displacement of the flexible membrane  122  outwardly from the reservoir  130 ; the larger the drop volume is ejected. Variable drop volume can be achieved when the inlet valve  124   a  and the outlet valve  124   b  have multiple actuation states as shown in  FIG. 1A through 1E . The ability to produce variable drop volume is beneficial to produce high quality print images by enabling more colors and higher levels of grey gradations. 
     In the above discussion of types of valves  124   a  and  124   b  (relative to  FIG. 1 ) several types of valve were mentioned, including a metal bi-morph, a metal tri-morph, a thermal actuator, an electrostatic actuator, a piezoelectric actuator, or a heater that boils the liquid to form a bubble to modulate the flow passing through the inlet channel  108  or the outlet channel  110 . Several of these types of valves are heat-actuated. For some embodiments of microfluidic drop ejector  134 , and particularly for embodiments that involve boiling a fluid to actuate the valve, the fluid flowing from inlet channel  108  to outlet channel  110  is preferably chosen to be a different fluid than ink  136 . In particular this fluid can be chosen to have a lower boiling point than that of the ink. In this way the valves  124   a  and  124   b  can be operated at lower energy than if they were in direct contact with ink  136 . In addition, less heat is dissipated near the valves in this case, so that ink does not kogate on or near the valve. Some examples of fluids having a low boiling point relative to the boiling point of water-based inks include ethanol (boiling point 78° C.), methanol (boiling point 65° C.) and 3M Fluorinert® liquids (boiling point adjustable to as low as 30° C.). 
     Typically a plurality of micro-fluidic drop ejectors  134  (for example, one hundred or more) are formed together as an array of micro-fluidic drop ejectors  134  on a printhead die. Because the portion of the micro-fluidic drop ejector  134  that is seen externally is the nozzle  132 , an array of micro-fluidic drop ejectors  134  is sometimes interchangeably referred to herein as a nozzle array (referred to as nozzle array  253  hereinbelow). 
     Referring to  FIG. 5  a perspective view of a portion of a printhead chassis  250  for use in an inkjet printer is shown. Although an inkjet printhead is shown, any suitable printhead may be used. Printhead chassis  250  includes two printhead die  251  that are affixed to a common mounting support member  255 . A printhead die  251  is an example of a printing device. Each printhead die  251  contains two nozzle arrays  253 , such as two arrays of micro-fluidic drop ejectors, so that printhead chassis  250  contains four nozzle arrays  253  (four arrays of micro-fluidic drop ejectors) altogether. The four nozzle arrays  253  in this example can each be connected to separate ink sources such as cyan, magenta, yellow, and black. Each of the four nozzle arrays  253  is disposed along nozzle array direction  254 , and the length of each nozzle array along 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 a recording medium  370  (see  FIG. 7 ). Following the printing of a swath, a recording medium  370  is advanced along a media advance direction that is substantially parallel to nozzle array direction  254 . 
     Also shown in  FIG. 5  is a flex circuit  257  to which the printhead die  251  are electrically interconnected, for example, by wire bonding or TAB bonding. The interconnections and interconnection pads (not shown) 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. 6 ), 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 . 
       FIG. 6  shows a portion of a desktop carriage printer. Some of the parts of the printer have been hidden in the view shown in  FIG. 6  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. 6 ) 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 . 
     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. 5 , 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. 6 . Multi-chamber ink supply  262 , for example, contains three ink sources: cyan, magenta, and yellow ink; while single-chamber ink supply  264  contains the ink source for 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 . 
     A variety of rollers are used to advance the medium through the printer as shown schematically in the side view of  FIG. 7 . 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. 6 ). 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  (see  FIG. 6 ) 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. 
     The motor that powers the paper advance rollers is not shown in  FIG. 6 , 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. 6 , is the maintenance station  330 . 
     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 for controlling the printing process, and an optional connector for a cable to a host computer. 
     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 
     
         
           102  actuator 
           104  member 
           106  pressure chamber 
           108  inlet channel 
           110  outlet channel 
           112  side wall 
           114  first portion 
           116  second portion 
           118  top enclosure 
           120  inflexible member 
           122  flexible member 
           124   a  valve 
           124   b  valve 
           126  protruding portion 
           128  protruding portion 
           130  inkjet reservoir 
           132  nozzle 
           134  micro-fluidic drop ejector 
           136  ink 
           138  ink droplet 
           200  carriage 
           250  printhead chassis 
           251  printhead die 
           253  nozzle array 
           254  nozzle array direction 
           255  mounting support member 
           256  encapsulant 
           257  flex circuit 
           258  connector board 
           262  multi-chamber ink supply 
           264  single-chamber ink supply 
           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  feedroller 
           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 
           370  stack of media 
           371  top piece of medium 
           380  carriage motor 
           382  guide rail 
           383  encoder fence 
           384  belt 
           390  electronics board 
           392  cable connectors