Abstract:
A method is disclosed. The method includes setting a desired flow rate for ink in an ink jet printer, measuring an actual flow rate of the ink, determining if the measured flow rate is equal to the desired flow rate and adjusting the flow rate if the measured flow rate is not equal to the desired flow rate.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to the field of ink jet printing systems. More particularly, the invention relates to ink flow supply within an ink jet printing system. 
       BACKGROUND 
       [0002]    An ink jet printer is as an example of a printing apparatus that ejects droplets of ink onto a recording medium such as a sheet of paper, for printing an image on the recording medium. The ink jet printer includes a print engine having at least one ink jet head provided with an ink cartridge that accommodates the ink. In operation of the print engine, the ink is supplied from the ink cartridge to ejection nozzles within each ink jet head, so that a printing operation is performed by ejection of the ink droplets from selected ejection nozzles. 
         [0003]    However, ink jet printers typically implement an uncompensated pressurized ink cartridge or positive pressure pump to supply ink to an ink reservoir or print head. This supply is typically provided without monitoring pressure or flow rate of the ink, or estimating the demand of ink prior to supply. These systems are demand based (e.g., supply ink after ink has been printed), and as a result, the ink supply system may falter, either due to insufficient ink flow, an oversupply of ink, or suffer from poor system response time. 
         [0004]    Therefore, a method to predict ink usage and regulate ink flow accordingly in an ink jet printer is desired. 
       SUMMARY 
       [0005]    In one embodiment, a method is disclosed. The method includes setting a desired flow rate for ink in an ink jet printer, measuring an actual flow rate of the ink, determining if the measured flow rate is equal to the desired flow rate and adjusting the flow rate if the measured flow rate is not equal to the desired flow rate. 
         [0006]    In further embodiment, a printer is disclosed. The printer includes a print engine including an ink jet print head having a plurality of ink nozzles; and a cartridge to supply ink to the print head. The printer further includes a control unit that provides feedforward dynamic control to regulate ink flow from the cartridge to the print head. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Embodiments of the present invention may be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the invention. The drawings, however, should not be taken to be limiting, but are for explanation and understanding only. 
           [0008]      FIG. 1  is a block diagram illustrating one embodiment of a print system; 
           [0009]      FIG. 2  illustrates one embodiment of a control system implemented by a control unit; and 
           [0010]      FIG. 3  is a flow diagram illustrating one embodiment of a process for regulating ink flow. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    An ink flow regulating mechanism is described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form to avoid obscuring the underlying principles of the present invention. 
         [0012]    Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
         [0013]      FIG. 1  illustrates one embodiment of a printing system  100 . Printing system  100  includes a print application  110 , a server  120  and a printer  130 . Print application  110  makes a request for the printing of a document. Print server  120  processes pages of output that mix all of the elements normally found in presentation documents, e.g., text in typographic fonts, electronic forms, graphics, image, lines, boxes, and bar codes. 
         [0014]    Print server  120  subsequently communicates with printer  130 . Printer  130  includes a control unit  140  and a print engine  160 . Control unit  140  receives print jobs into printer  130 . Further, control unit  140  processes and renders objects received from print server  120  and provides sheet side maps for printing to print engine  160 . Print engine  160  provides an imaging process to mark a printable recording medium (e.g., paper). 
         [0015]    In one embodiment, print engine  160  includes a cartridge  170 , flow sensor  180 , ink reservoir  185  and print heads  190 . Cartridge  170  supplies ink to ink reservoir  185 , which is then provided to print heads  190 . In other embodiments, flow sensor  180  and reservoir  185  may be combined into a single device where flow rate is correlated to the rate of change of ink volume (or equivalent parameter such as height of ink in reservoir  185 ). According to one embodiment, print heads  190  are fixed, wide-array ink jet print heads including one or more nozzles that are implemented to spray droplets of ink onto a sheet of paper in order to execute a print job. However, print heads  190  may include other types of ink jet print heads, as well as a moving print head design. 
         [0016]    In one embodiment, flow sensor  180  measures the flow of ink from cartridge  170  to print heads  190 . In such an embodiment, control unit  140  continuously monitors the flow rate of ink measured at flow sensor  180  in order to regulate the ink flow. In a further embodiment, the ink flow is regulated by adjusting cartridge  170  pressure or via a positive pressure pumping device to either increase or decrease pressure based on flow measured at flow sensor  180 . 
         [0017]    In a further embodiment, control unit  140  analyzes information associated with each print job received in order to estimate an amount of ink that is to be supplied from cartridge  170 . Control unit  140  performs the analysis of the ink usage estimate for every individual sheet side prior to transmitting the sheet side print job data to print engine  160 . Because the estimate is calculated in advance of the actual ink demand by print head  190 , the ink demand information is optimally delayed to minimize ink pressure gradient at reservoir  185  and at printhead  190  achieving an optimal ink flow. 
         [0018]    The optimal delay may appear as a combination of a fixed time delay and a variable delay. The variable delay is a function of the print job complexity where each sheet side of the individual print jobs is tracked through the processing path including a buffer. The buffer is used to ensure sheet side data is available for print engine  160  when requested. 
         [0019]    The fixed time is the portion of the data processing path where the sheet side data is transmitted to print head  190  and the actual data processing time is predictable consistent with print engine  160  process controls (e.g., data arrives at print head  190  at the exact moment to place each individual drop on the paper at the correct paper location. In one embodiment, drops may be a single volume or different volumes dependent on print engine design. 
         [0020]    The ink usage estimate appears effectively as a real time estimate to the ink flow system, thereby reducing overall system response time. In one embodiment, the optimal delay may also incorporate physical ink supply system response delays based on known electrical, mechanical and fluid properties of the system. Thus a variable ink flow is provided to match actual ink demand. 
         [0021]      FIG. 2  illustrates one embodiment of a control system  200  implemented by control unit  140 . As shown in  FIG. 2 , the control system includes a feedback system based on a measured flow rate, and a feed forward system based on the ink usage estimation and optimal timing. The flow rate from cartridge  170  is adjusted accordingly based on each system. 
         [0022]      FIG. 3  is a flow diagram for one embodiment of a process for regulating ink flow. At processing block  310 , control unit  140  receives information for a new print job to be printed. At processing block  320 , control unit  140  estimates a volume of ink that will be needed for each sheet side to print the print job. At processing block  330 , a desired ink flow rate for each sheet side the print job is set based upon the estimated ink usage after the appropriate delay (e.g., the optimal delay previously discussed above) to approximately coincide with the printing of the actual sheet side data. 
         [0023]    At processing block  340 , an ink flow output from cartridge  170  begins at the desired rate. At processing block  350 , the actual flow rate measured at flow sensor  180  is monitored. At decision block  360 , it is determined whether the measured flow rate is equal to the desired flow rate. If so, it is determined whether the print job has completed, decision block  370 . If the print job has not been completed, control is returned to processing block  320  where the ink usage estimate is recalculated for the remaining individual sheet sides for the print job and the process is repeated from that point. 
         [0024]    If at decision block  360 , it is determined that the measured flow rate does not equal the desired flow rate, cartridge  170  output flow rate is adjusted accordingly. For instance, in one embodiment, if the measured flow rate is less than the desired flow rate, the pressure is increased. Conversely, in the same embodiment, if the measured flow rate is greater than the desired flow rate, the pressure is reduced. Subsequently, it is determined at decision block  370  whether the print job has completed. If the print job has completed, control is returned to processing block  310  for a subsequent print job. 
         [0025]    Although described with an embodiment implementing variable ink flow rate and variable pressure based on reservoir fill time, other embodiments may implement a constant ink flow rate with constant pressure and a variable reservoir volume. The above-described mechanism therefore controls ink flow to an ink jet reservoir to ensure that the reservoir is adequately filled to supply the estimated ink demand. 
         [0026]    Embodiments of the invention may include various steps as set forth above. The steps may be embodied in machine-executable instructions. The instructions can be used to cause a general-purpose or special-purpose processor to perform certain steps. Alternatively, these steps may be performed by specific hardware components that contain hardwired logic for performing the steps, or by any combination of programmed computer components and custom hardware components. 
         [0027]    Elements of the present invention may also be provided as a machine-readable medium for storing the machine-executable instructions. The machine-readable medium may include, but is not limited to, floppy diskettes, optical disks, CD-ROMs, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, propagation media or other type of media/machine-readable medium suitable for storing electronic instructions. For example, the present invention may be downloaded as a computer program which may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals embodied in a carrier wave or other propagation medium via a communication link (e.g., a modem or network connection). 
         [0028]    Throughout the foregoing description, for the purposes of explanation, numerous specific details were set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention may be practiced without some of these specific details. Accordingly, the scope and spirit of the invention should be judged in terms of the claims which follow.