Abstract:
A fluid ejecting method and system include one or more fluid ejectors within a fluid ejector frame and an interposer frame and movably mounted upon a fluid ejector carriage. The fluid ejector carriage traverses across a recording medium for placing swaths of fluid droplets upon the recording medium. A biasing structure urges the fluid ejector frame to a first position to obtain highly accurate and repeatable placement of fluid droplets when the fluid ejector frame is in the first position. A second position of the fluid ejector frame is achieved by energizing a position actuator to move the fluid ejector frame from the first position to the second position to obtain highly accurate and repeatable placement of fluid droplets when the fluid ejector frame is in the second position. The recording medium is advanced separately upon completing a set of at least one swath of fluid droplets.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of Invention  
           [0002]    This invention relates to mechanisms and methods for advancing a fluid ejection system relative to a receiving medium.  
           [0003]    2. Description of Related Art  
           [0004]    Partial width fluid ejection systems are known to use an advance mechanism that advances a receiving medium relative to a fluid ejector head in a process, or slow scan, direction in conjunction with a carriage that moves along a fast scan direction to facilitate ejecting fluid onto the receiving medium. In a typical fluid ejecting system using this combination of movements between the advance mechanism and the carriage, the advance mechanism moves the receiving medium in a direction perpendicular to the direction of movement of the carriage along the fast scan direction. The carriage houses at least one fluid ejector having a plurality of fluid-ejecting nozzles from which droplets of fluid are placed on the receiving medium in swaths according to the transversing movement of the carriage in the fast scan direction across the receiving medium. The receiving medium advance motion and the carriage motion are coordinated to the extent that the receiving medium advance is stopped while the carriage travels across the receiving medium to place fluid upon the receiving medium.  
           [0005]    A variety of configurations have been used to date to provide the dual motions necessary for placing the ejecting fluid upon the receiving medium using a carriage. For example, some known systems use a servo-system including an encoder to accurately move a receiving medium in two modes. The first mode advances the receiving medium a designated distance at the completion of each swath of ejected fluid from the one or more fluid ejector on the carriage. The servo motor provides the first motion mode for advancing the receiving medium. The servo motor provides a second, finer, motion mode to the receiving medium as well. The second, finer, motion mode positions the receiving medium a necessary, though relatively smaller, distance compared to the first advance distance the receiving medium is moved as provided by the servo-motor. The second, finer, motion aligns the recording medium relative to the one or more fluid ejector for receiving second, or subsequent, swaths off fluid ejected from the one or more fluid ejector.  
           [0006]    Thus, the dual movements in this servo-motor system require fairly precise co-ordination between the servo-motor and the receiving medium relative to the one or more fluid ejectors. However, servo-motors are prone to deviations in placing the receiving medium, resulting in less accurate placement of fluid upon the receiving medium. Moreover, in those servo-motor printing systems that move the receiving medium in the advance directions in two modes, the accuracy of movement is questionable as well, since it is very difficult to move the receiving medium consistently in the second mode the designated distance W when the distance is an increment perhaps as small as {fraction (1/600)} inch. Moving the recording media such a small distance requires precision media drive rolls, gears, encoders and motors, which add to the cost and complexity of a fluid ejecting system. Moreover, the flexible qualities of recording media render recording media susceptible to positioning variations that are difficult to predict or compensate for, even in a fluid ejecting system that uses high precision elements. A stepper motor could also be used to perform the same dual motions. However, the same or similar problems often occur in stepper motor systems.  
           [0007]    Alternatively, some known fluid ejecting systems use a ball and screw carriage advance mechanism, as opposed to the recording media advance mechanism discussed above. The ball and screw carriage advance mechanism is used with a high degree stepping motor that incrementally moves the fluid ejectors when the carriage has completed placing a swath of fluid upon a receiving media. In such a system, the carriage is moved along support rails by operating the ball and screw, to scan the carriage across the receiving medium. The receiving medium remains stationary thoughout the fluid ejecting process. Thus, all the movements in this ball and screw type printing system are by the carriage and fluid ejectors.  
           [0008]    A more recent trend among fluid ejecting systems is to use the same general configurations as discussed above, but to increase the number of ejecting nozzles on the fluid ejector while using the same fluid ejector dimensions. The increase in fluid-ejecting nozzles results in a resolution as high as 600 dots per inch (dpi) versus the standard 300 dpi resolution used in earlier fluid ejecting systems. However, the increased number of fluid-ejecting nozzles is not easily achieved. In particular, the precision required for manufacturing fluid-ejecting nozzles has become increasingly more difficult to attain, since an increased number of nozzles is required to provide up to 600 dpi resolution on the same sized fluid-ejector that may have originally provided only enough nozzles for 300 dpi resolution. Thus, the nozzles necessarily become smaller and more difficult to make.  
         SUMMARY OF THE INVENTION  
         [0009]    The above-described prior fluid ejecting systems provide variations of the dual motions along the advance direction needed by the carriage and its fluid ejectors relative to the receiving medium. The servo-motor systems provide movements quickly, but not necessarily accurately. The ball and screw systems provide accuracy but not quickness. Systems increasing the fluid ejecting nozzles on a standard dimensioned fluid ejector result in excess manufacturing and replacement costs.  
           [0010]    Accordingly, a need exists for a fluid ejecting system providing a quick, accurate and inexpensive manner of achieving the necessary dual motions of the carriage and its fluid ejector relative to a receiving medium.  
           [0011]    In various exemplary embodiments of the fluid ejecting system and methods of this invention, a fluid ejector and carriage are mounted within an interposer frame that is movable along support rails. A separate paper advance mechanism advances the receiving medium a designated distance when a swath is completed. In operation, the receiving medium advances to an initial position for receiving fluid from the fluid ejector, where the fluid ejector is in a first position within the interposer frame. The fluid ejector is biased against a first set of surfaces in the first position by a biasing element. This tends to ensure the fluid is consistently and accurately placed upon the receiving medium as droplets of fluid are ejected from the fluid ejector located in the first position as printing information upon the receiving medium. A spring, for example, may be used as the biasing element. With the fluid ejector in the first position, the carriage travels across the receiving medium, depositing droplets of fluid onto the receiving medium in a swath.  
           [0012]    Upon completion of that swath, a position actuator, for example, is energized to urge the fluid ejector to a second position, where the fluid ejector is located against a second set of surfaces. In the second position, the fluid ejector ejects a second swath upon the receiving medium. Thus, whenever the fluid ejector is placed in the second position, the accuracy of placing fluid upon the receiving medium that is achieved is similar to the accuracy achieved by biasing the fluid ejector to the first position. The fluid placement accuracy is achieved regardless of the number, or direction, of swaths being ejected due to consistently placing the fluid ejector against the first and second sets of surfaces corresponding to the first and second positions, respectively.  
           [0013]    After a pair of first and second swaths are completed, the receiving medium is advanced to a next position to perform another swath, or pair of swaths, as desired. Thus, the advancing of the receiving medium is easily co-ordinated with the completion of a swath. Moreover, the incremental movement of the fluid-ejector is easily and quickly performed to either of the first and second positions.  
           [0014]    Sensors may be used to detect the positioning of the fluid ejector relative to the receiving media, or to provide feedback to a processing system, if, for example, variations in swath widths are desired or other positional information is needed to cause the position actuator to operate and move the fluid ejector to/from either of a first or second position, or to any other fractional part of the distance between either of the first or second positions. After completion of the desired swath or set of swaths, the receiving medium is advanced to place an additional swath or set of swaths of fluid upon the receiving medium as desired.  
           [0015]    Alternatively, a fixed fluid ejector may be used in conjunction with an adjustable fluid ejector to place fluid upon a recording medium, wherein a sensor detects the alignment necessary for the adjustable fluid ejector to place fluid in an appropriate location upon the recording medium relative to the fluid placed upon the recording medium by the fixed fluid ejector. The sensor may be, for example, a position sensor using position sensing diodes, such as the position sensor made by Hammamatsu Inc., Japan. Many other sensor types can also be used; such as laser micrometers, or eddy current position sensors, for example.  
           [0016]    Upon detection of the necessary alignment adjustment distance, at least one position actuator is energized to move the adjustable fluid ejector the necessary alignment distance to place fluid upon the recording medium in a swath subsequent to the swath of fluid placed upon the recording medium by the fixed fluid ejector. Similarly, as above, the receiving medium is advanced after completion of the swath or set of swaths of fluid upon the receiving medium, as desired.  
           [0017]    In various exemplary embodiments, the system and methods according to this invention provides a sequence of synchronized dual motions that are easily performed and are accurately repeatable, while providing a relatively quick fluid ejection process. Moreover, this invention uses structures that are inexpensive to produce, maintain or replace.  
           [0018]    These and other features and advantages of this invention are described in, or are apparent from, the detailed description of various exemplary embodiments of the systems and methods according to this invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    Various exemplary embodiments of this invention will be described in detail with reference to the following figures, wherein like numerals represent like elements, and wherein:  
         [0020]    [0020]FIG. 1 is a cutaway view of a fluid-ejector and carriage mounted upon support Grails in a conventional fluid-ejecting system;  
         [0021]    [0021]FIG. 2 illustrates one exemplary embodiment of the carriage and fluid-ejector structures according to this invention;  
         [0022]    [0022]FIG. 3 illustrates another view of an exemplary embodiment of the carriage, one fluid-ejector structure and support rails according to this invention;  
         [0023]    [0023]FIG. 4 illustrates another exemplary embodiment using displacement sensors and a processing system according to this invention; and  
         [0024]    [0024]FIG. 5 illustrates another exemplary embodiment using a fixed fluid ejector and an adjustable fluid ejector according to this invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0025]    [0025]FIG. 1 shows a schematic view of one exemplary embodiment of an exemplary fluid ejection system  10 . A fluid ejector  12  includes one or more linear arrays of fluid-droplet producing channels housed within one or more printheads  14 . The fluid ejector  12  is mounted upon a reciprocal carriage  16  that is movable upon support rails  18 . Fluid droplets  20  are placed, for example, as printing information, upon a recording medium  22  each time the fluid ejector  12  traverses across the recording medium  22  along a fast scan direction, or axis, A. At the completion of a swath, the recording medium  22  is then stepped, or moved, in a slow scan, or process, direction B to receive a next swath of the fluid droplets. Advancing the recording medium  22  may be achieved by a motorized take-up roll or any other appropriate known or later developed structures, apparatuses or devices. The fluid ejector  12  traverses across the recording medium  22  along the fast scan axis A, for example, by using any appropriate known or later developed drive mechanisms, structures or apparatuses. The drive mechanism may be operatively connected to a controller  24  to selectively cause the fluid ejector  12  and carriage  16  to traverse across the recording medium  22 .  
         [0026]    [0026]FIG. 2 shows one exemplary embodiment of the systems and methods for performing the motions of the fluid ejectors  14  and the fluid ejector carriage  12  according to this invention. The fluid ejector carriage  12  includes an interposer frame  35  having first and second pairs of surfaces  36  and  37  protruding from interior surfaces of, for example, the top and bottom sides of the interposer frame  35  with reference to direction B. A fluid ejector frame  38  is positioned within the interposer frame  35  and the protruding surfaces  36  and  37 . The fluid ejector frame  38  includes first and second pairs of locator surfaces  39  and  40  that oppose the corresponding protruding surfaces  36  and  37 , respectively.  
         [0027]    The fluid ejector frame  38  is urged to either of a first position or a second position. The fluid ejector frame  38  is urged toward the first or second position by one or more biasing elements, such as for example, one or more springs  41 . For example, the one or more springs  41  can thus bias the fluid ejector frame  38  and specifically the first pair of locator surfaces  39  against the corresponding protruding surfaces  36  of the interposer frame  35  to place the fluid ejector frame  38  into, for example, the first position. When in the first position, the locator surfaces  39  of the fluid ejector frame  38  abut securely against the corresponding protruding surfaces  36  of the interposer frame  35 . At the same time, a gap  31  exists between the upper portion of the fluid ejector frame  38  such that the locator surfaces  40  are, for example, {fraction (1/600)} inch apart from the corresponding protruding surfaces  37  of the interposer frame  35 .  
         [0028]    Upon completion of, for example, a first pass of a current swath, a position actuator  42  is energized to urge the fluid ejector frame  38  towards the second position. In this second position, the spring  41  is compressed and the fluid ejector frame  38  moves to close the gap  31  such that the locator surfaces  40  abut securely against the corresponding protruding surfaces  37  of the interposer frame  35 . At the same time, the gap  31  is provided between the lower locator surfaces  39  and the corresponding protruding surfaces  36  of the interposer frame  35 .  
         [0029]    [0029]FIG. 3 shows the related structures for performing the motions of the fluid ejectors  14  and the fluid ejector carriage  12  according to the first exemplary embodiment of this invention. As shown in FIG. 2, the fluid ejectors  14  are located within the fluid ejector frame  38  and the interposer frame  35 , which is mounted upon the fluid ejector carriage  12 . The fluid ejector carriage  12  is movably mounted upon support rails  18  via a number of bearings  32 . The fluid ejector frame  38  is shown, for example, in the first position. The gap  31 , which is, for example, {fraction (1/600)} inch, is located between the protruding surfaces  37  and the locator surfaces  40  of the interposer frame  35  and the fluid ejector frame  38 , respectively. A first swath of fluid droplets is ejected from fluid ejectors  14  as the fluid ejector frame  38  and fluid ejector carriage  12  moves, for example, from left to right, across a recording medium  22  along the fast scan direction, or axis, A.  
         [0030]    Upon completing the first swath, the fluid ejector frame  38  is urged by the position actuator  42  to the second position within the interposer frame  35 . When in the second position, the gap  31  is no longer positioned between the protruding surfaces  37  and the locator surfaces  40 . Instead the gap  31  is now positioned between the protruding surfaces  36  and the locator surfaces  39 . Once the fluid ejector frame  38  is in the second position, a second swath of fluid droplets is ejected from fluid ejectors  14  as the fluid ejector frame  38  and fluid ejector carriage  12  again move across the recording medium  22  along the fast scan direction, or axis, A.  
         [0031]    It should be appreciated that the fluid ejectors  14  place the droplets of fluid in swaths upon the receiving medium  22  according to the location and motions of the fluid ejector frame  38  and fluid ejector carriage  12  as the fluid ejectors  14 , fluid ejector frame  38  and fluid ejector carriage  12  move along the support rails  18  across the receiving medium  22 . Thus, a first swath of fluid droplets may be placed upon the receiving medium  22  as the one or more fluid ejectors  14  move, for example, from left to right across the receiving medium  22  along the fast scan direction, or axis, A. Thus, upon completing the first swath of fluid droplets, the second swath of fluid droplets are placed upon the receiving medium  22  by moving the fluid ejectors  14 , fluid ejector frame  38  and fluid ejector carriage  12 , for example, from right to left across the receiving medium  22  along the fast scan direction, or axis, A.  
         [0032]    Alternatively, to perform the second swath the fluid ejectors  14 , fluid ejector frame  38  and fluid ejector carriage  12  are returned to, for example, the leftmost position along the rails  18  upon completing the first swath. Thus, the second swath of fluid droplets is placed upon the receiving medium  22  by moving the fluid ejectors  14 , fluid ejector frame  38  and fluid ejector carriage  12  from left to right across the receiving medium  22  along the fast scan direction, or axis, A similar to the manner in which the first swath of fluid droplets was placed upon the receiving medium  22 .  
         [0033]    In either case, upon completing, for example, the second, or subsequent, swath, the receiving medium  22  is advanced in the slow-scan, or process, direction B perpendicular to the fast scan direction, or axis, A. Of course, the orientations of the fast scan direction, or axis, A and the process direction B are exemplary only, and other orientations relative to one another are contemplated as within the scope and spirit of the invention.  
         [0034]    While the spring  41  is shown as the biasing member in FIGS. 2 and 3, any appropriate known or later developed structure may be used to urge the fluid ejector frame  38  to one of the first and second positions.  
         [0035]    Further, it should be appreciated that the position actuator  42  identified above is exemplary only. Any appropriate known or later developed structure or combination of structures may be used to urge the fluid ejector frame  38  from the one of the first and second positions to the other of the first and second positions, similarly, to the actuator  42  set forth in the exemplary embodiment described above.  
         [0036]    Still further, it should be appreciated that a single actuator, such as for example, a piezo-electric actuator may be used to perform the position actuating and biasing functions that have otherwise been described as individually performed by the position actuator  42  and biasing elements, such as for example, springs  41 .  
         [0037]    [0037]FIG. 4 shows another exemplary embodiment of the systems and methods according to this invention. The exemplary embodiment shown in FIG. 4 includes, for example, a sensor  50  that accurately detects the position, or displacement, of the receiving medium  22  before, during and/or after a swath of fluid droplets is placed upon the receiving medium  22 . The displacement data received by the sensor  50  is communicated to a processor  52 , which adjusts the position of the one or more fluid ejectors  14  by adjusting the fluid ejector frame  38  relative to the receiving medium  22 . At least one biasing element, such as, for example, the one or more springs  41 , and the actuator  42  cooperate to urge the fluid ejector frame  38  to a desired position, such as, for example, from which fluid droplets are ejected from the one or more fluid ejectors  14  onto the receiving medium  22 .  
         [0038]    Upon completing the first swath, for example, the sensor  50  determines the position of the fluid ejector frame  38  relative to the receiving medium  22 . The position information is transmitted to the processor  52 , which determines an amount of movement of the fluid ejector frame  38  desirable to adjust the position of the fluid ejector frame  38  so that a next swath of fluid droplets is accurately placed upon the receiving medium  22 . The determined adjustment of the processor  52  is relayed to one or more position actuators  42  that energize to move the fluid ejector frame  38  according to the determined adjustment.  
         [0039]    Of course, it should be appreciated that the configuration illustrated in FIG. 4 could as well provide that the sensor  50  detects the position of the one or more fluid ejectors  14  within the fluid ejection frame  38  relative to the fixed frame  12 , rather than relative to the receiving medium  22 . The fluid ejector frame  38  and the one or more fluid ejectors  14  could be incrementally positioned relative to the fixed frame  12  according to the position detection by the sensor  50  and as urged by the position actuator  42 . As a result, the same or similar print addressibility can be achieved.  
         [0040]    Thus, in contrast to the first exemplary embodiment outlined above with respect to FIGS. 1 and 2, no locating surfaces  39 ,  40  or protruding surfaces  36 ,  37  are used to limit the position the fluid ejector frame  38  may be placed into by, for example, the biasing element  41  or the position actuator  42 . Accordingly, greater sensitivity or variations in the position of the fluid ejector frame  38  in the slow scan direction B relative to the receiving medium  22  can be obtained to achieve the desired fluid droplet coverage on the receiving medium  22  desired. For example, the fluid ejector frame  38  may be moved in increments, such as, for example, {fraction (1/150)}″, {fraction (1/300)}″, {fraction (1/600)}″, {fraction (1/1200,)}″ etc., to vary the print addressibility in the slow scan direction.  
         [0041]    Similarly to the first exemplary embodiment, in this second exemplary embodiment, the receiving medium  22  remains stationary as the fluid ejector frame  38  and fluid ejector carriage  12  move from one position to another position. Upon completing, for example, a second swath of fluid droplets placed upon the receiving medium  22 , the receiving medium  22  is advanced a designated distance in the processing direction B. Then, the sensing and adjusting of the fluid ejector frame  38 , relative to the receiving medium  22 , is repeated until the desired fluid droplet coverage upon the receiving medium  22  is achieved. Alternatively, in other exemplary embodiments, only the fluid ejector frame  38  is moved relative to a fixed fluid ejector carriage  12  while the receiving medium  22  remains stationary until the desired fluid droplet coverage upon the receiving medium  22  is achieved.  
         [0042]    [0042]FIG. 5 shows yet a third exemplary embodiment of the systems and methods according to this invention. The third exemplary embodiment shown in FIG. 5 includes a fixed fluid ejector frame  60  and an adjustable fluid ejector frame  38 . The adjustable fluid ejector frame  38  is movably adjusted by a pair of biasing elements, such as, for example, one or more springs  41  provided on one pair of adjacent sides of the adjustable fluid ejector frame  38 . A corresponding pair of position actuators  42  are provided on the other pair of adjacent sides of the adjustable fluid ejector frame  38 . The pair of biasing elements, for example, the one or more springs  41 , and the pair of position actuators  42  are thus disposed between the fluid ejector frame  38  and the fluid ejector carriage  12 .  
         [0043]    It should be appreciated that the biasing elements may be on the same side as the position actuators. Further, the biasing elements may be “combined” with the position actuators, such as, for example, where at least one spring is adjacent to, or is around, the biasing element. Still further, the biasing elements may be integral with the position actuators, wherein the biasing function is also performed by the position actuators.  
         [0044]    A receiving medium  22  is positioned to receive fluid droplets ejected from fluid ejectors within the fixed fluid ejector frame  60  and the adjustable fluid ejector frame  38 . The recording medium is stationary while the fluid droplets are ejected from the fluid ejectors within the fixed fluid ejector frame  60  and the adjustable fluid ejector frame  38 . However, the receiving medium  22  is advanced in the processing direction B when a swath of ejected fluid droplets of a desired width in the fast scan direction, or axis, A across the receiving medium  22  is completed.  
         [0045]    A control system  64  connected to a sensor  62  monitors the position of the adjustable fluid ejector frame  38  relative to the fixed fluid ejector frame  60  as fluid droplet ejection in swaths upon the receiving medium  22  occurs. For example, after the fluid ejectors within the fixed fluid ejector frame  60  eject an initial swath of fluid droplets upon the receiving medium  22 , the sensor  62  determines the location the adjustable fluid ejector frame  38  must assume to align the second, or subsequent, swath of fluid droplets with the initial, or preceding, swath of fluid droplets ejected upon the receiving medium  22 . The controller  64  therefore energizes the position actuators  42  to move the adjustable fluid ejector frame  38  to the desired location. As a result, the fluid ejector  38  may be moved in increments, such as, for example, {fraction (1/150)}″, {fraction (1/300)}″, {fraction (1/600)}″, {fraction (1/1200)}″, etc., to vary the print addressibility in the slow scan direction B.  
         [0046]    The position actuators  42  move the adjustable fluid ejector frame  38  in either, or both, of the processing direction B and fast scan direction, or axis, A. The biasing elements, for example springs  41 , act in compliance with the position actuators  42  to position the adjustable fluid ejector frame  38  appropriately relative to the fixed fluid ejector frame  60 . Once the adjustable fluid ejector frame  38  has reached the desired location, the second, or subsequent, swath of fluid droplets is ejected upon the receiving medium  22 . As a result, the second, or subsequent, swath of fluid droplets ejected upon the recording medium is in appropriate alignment with the initial, or preceding, swath of fluid droplets.  
         [0047]    Thus, again in contrast to the first embodiment, the alignment of the adjustable fluid ejector frame  38  of the third embodiment is achieved without the locating surfaces  39  and  40  or the protruding surfaces  36  and  37 . Instead, the control system  64  moves the adjustable fluid ejector frame  38  in the processing direction B and fast scan direction, or axis, A by energizing the position actuators  42  to position the adjustable fluid ejector frame  38  appropriately.  
         [0048]    While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.