Abstract:
The present invention is embodied in a system and method for implementing spit strips to reduce service station fluid waste, and to improve throughput. The printing system includes a controller, printhead assembly, and a service station assembly, operating to produce an image on a print media. The operations of the system are produced by controlling the direction of a motor. First, a portion of ink in the nozzles that have become dye enriched are determined and then the dye enriched ink is purged on available margins on a periphery of print media outside an area reserved for images.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention generally relates to inkjet printers and in particular to a system and method for implementing spit strips to reduce service station fluid waste, to improve throughput and to minimize servicing aerosol.  
         BACKGROUND OF THE INVENTION  
         [0002]    Conventional ink jet print engines typically contain three primary components generally organized in series. The platen and the service station are included among these components. The platen has a printing area upon which the print media are printed. The service station includes a spittoon receptacle in which print drops are disposed to clear the nozzles. The service station also contains a wiper to wipe clean the printhead during use and a cap to prevent the printhead from drying out during periods of inactivity.  
           [0003]    One common problem that ink jet printers encounter is that the ink nozzles of the ink jet printer frequently become plugged or otherwise contaminated with a variety of contaminants, such as dried ink and paper fibers. These contaminants can crust the nozzle internally and externally, preventing the nozzles from operating correctly and in turn lowering the quality of print on the print media. The service station is used to service a printhead to keep the nozzles operating properly.  
           [0004]    A typical function of the service station is capping. Capping prevents the printhead from drying out when not in use. Capping uses a cap to provide a seal between the vaporization chamber and the printhead. Capping prevents ink from being drawn by capillary action from within the ink supply through the printhead. Another function of the service station is known as wiping. This function uses a wiping action to remove external debris and contaminants from the nozzles. Ink used in ink jet printers is designed to dry quickly and permanently, and if allowed to dry on the nozzles and not wiped away becomes difficult to remove.  
           [0005]    Ink jet printer service stations may be implemented in a plurality of ways. For instance, one type of service station is a passive service station that does not use a motor. Passive service stations, however, are noisy and not very effective, which can lower print quality and shorten printhead life. Another type of service station design uses a motor to operate the service station and a separate motor to feed paper through the printer. There are several problems, however by using a motor to feed the paper and a motor to operate the service station, the printer will be more costly and heavier.  
           [0006]    Other service stations generally include a spittoon receptacle in which print drops are disposed to clear the nozzles. The spittoon is conventionally added to the printer increasing the lateral traverse of the throughput through increased scan width. However, the over travel of this type of service station with the spittoon can be problematic. Another problem is the increase in aerosol accumulation of ink on the printer from particulates that do not have the momentum to reach the spittoons. Also, the concentrated ink from a spittoon can be difficult and time consuming to dispose. Further, in some environments, the spittoon can be considered hazardous waste by regulator standards. Therefore, what is needed is a system and method that solves these problems.  
         SUMMARY OF THE INVENTION  
         [0007]    To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention is embodied in a system and method for implementing spit strips to reduce service station fluid waste, and to improve throughput.  
           [0008]    The printing system includes a controller, printhead assembly, and a service station assembly, operating to produce an image on a print media. At the start of a printing operation, a first swath either fires ink into a spittoon and then continues printing the image, or fires ink on a leading edge spit strip. The spit strip can be defined as the height of the printhead divided by number of passes for a given printmode being used. On normal swaths, the printhead can produce an image within the margin of the print image on the print media.  
           [0009]    In an alternative embodiment, nozzles not being used to print the image on the particular swath will fire outside the image margins onto spit strips. In another alternative embodiment, additionally, on predetermined swaths, the carriage can revert to a wide traverse and nozzles will eject inks into the spittoons. In another embodiment, since spit strips are used, the printer does not include a spittoon.  
           [0010]    The invention maintains image quality on the print media afforded by a spittoon, and with a decrease in the difficulty and time required to dispose of ink from the spittoon as part of the service station system. The invention also decreases the quantity of aerosol accumulation of ink on the printing system. The present invention purges the portion of ink in the nozzles that have become dye enriched. Dye enrichment is caused by the evaporation of ink vehicle through nozzles to create overly concentrated ink, which in turn can cause dark corners on the printed document. This is advantageous because using the dye enriched ink on a portion of a document creates an image quality defect in that portion of the document, which is avoided by the present invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The present invention can be further understood by reference to the following description and attached drawings that illustrate the preferred embodiment. Other features and advantages will be apparent from the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.  
         [0012]    [0012]FIG. 1 shows a block diagram of an overall printing system incorporating the present invention.  
         [0013]    [0013]FIG. 2 is an exemplary printing device that incorporates the invention and is shown for illustrative purposes only.  
         [0014]    [0014]FIG. 3 is a detailed flow diagram illustrating the operation of the present invention.  
         [0015]    [0015]FIG. 4 is a block diagram illustrating the relationship between print swaths and the printhead assembly.  
         [0016]    [0016]FIG. 5 is a block diagram illustrating the interaction between the components of the controller and the print swaths of the printing system.  
         [0017]    [0017]FIG. 6 is a pictorial diagram illustrating the spit strips disposed on print media with an image. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    In the following description of the invention, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration a specific example in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.  
         [0019]    I. General Overview  
         [0020]    [0020]FIG. 1 is an overall block diagram of overall printing system incorporating the present invention. In general, the printing system  100  can be used for printing a material (such as ink) onto a print media, which can be paper. The printing system  100  is electronically coupled to a host system  106 , which can be a computer or microprocessor for producing print data for the printing system  100  to print.  
         [0021]    The printing system  100  includes a controller  112  coupled to an ink supply device  118 , a power supply  124  and a printhead assembly  130 . The printhead assembly  130  generally includes a printhead (not shown) and a carriage assembly (not shown) that allows the printhead to traverse across the print media. The ink supply device  118  is fluidically coupled to the printhead assembly  130 . A motor  136 , which receives power from the power supply  124 , is coupled to a print media feed assembly  142  and a service station drive assembly  148 .  
         [0022]    Although only one motor  136  is shown, the printing system  100  may include a plurality of other motors that perform various other functions (such as a paper pick-up motor to pick-up paper from a paper storage tray). The direction of the motor  136  is controlled by a motor direction controller  154  that is coupled to the controller  112 . A print media source  160  supplies a print media (not shown) to the print media feed assembly  142 . A service station assembly  166 , can include a capping assembly  172  and a wiping assembly  178 , is coupled to the service station drive assembly  148  and interacts with the printhead assembly  130 .  
         [0023]    The system  100  uses the above described components of FIG. 1 to determine the portion of ink in the nozzles that have become dye enriched and purge this portion on available margins on a periphery of print media outside an area reserved for images. The portion of dye enriched ink can be determined by given parameters, such as with empirical data, with arbitrary estimations or with user configured data. This purging decreases the quantity of aerosol accumulation of ink on the printing system. Dye enrichment is caused by the evaporation of ink vehicle through nozzles to create overly concentrated ink, which in turn can cause dark corners on the printed document. This is advantageous because using the dye enriched ink on a portion of a document creates an image quality defect in that portion of the document, which is avoided by the present invention.  
         [0024]    During operation of the printing system  100 , the power supply  124  provides a controlled voltage to the controller  112  and the motor  136 . The controller  112  receives the print data from the host system  106  and processes the print data into printer control information and image data. The processed data, image data and other static and dynamically generated data are exchanged with the ink supply device  118  and the printhead assembly  130  for controlling the printing system  100 .  
         [0025]    The printhead assembly  130  receives ink from the ink supply device  118  and prints by ejecting the ink through the printhead assembly  130  onto a print media (such as paper). The print media is supplied by the print media source  160  and transported to the printhead assembly  130  at least in part by the print media feed assembly  142 . The motor  136  drives the print media feed assembly  142  and provides a means to transport the print media from the print media source  160  to the printhead assembly  130 . The motor  136  also drives the service station drive assembly  148 , which provides control of the service station assembly  166  including the capping assembly  172  and the wiping assembly  178 . Generally, when the service station drive assembly  148  is engaged with the motor  136 , the capping assembly  172  and wiping assembly  178  are active and the service station drive assembly  148  provides precise positioning control to allow the printhead assembly  130  to be capped and wiped. The engagement and disengagement of the motor  136  with the print feed media assembly  142  and the service station drive assembly  148  is achieved in part using the motor direction controller  154 .  
         [0026]    For example, if the printing system  100  is performing a print media feed operation and the printhead assembly  130  needs service station operations performed, the motor direction controller  154  disengages the print media feed assembly  142  and engages the service station drive assembly  148  by momentarily reversing the direction of the motor  136  (generally less than one full revolution). Similarly, after the service station operations have been performed the motor direction controller  154  disengages the service station drive assembly  148  and engages the print media feed assembly  142  by again momentarily reversing the direction of the motor  136 .  
         [0027]    Thus, the motor  136  is used both to transport the print media to the printhead assembly  130  and to operate the service station assembly  166  while precisely controlling the positioning of the capping assembly  172  and the wiping assembly  178  relative to the printhead assembly  130 . The motor  136  can be used to perform both of these tasks because in general the print media will not be advanced in the printing system  100  while the printhead assembly  130  is being serviced by the service station assembly  166 .  
         [0028]    II. Exemplary Printing System  
         [0029]    [0029]FIG. 2 is an exemplary printing device that incorporates the present invention and is shown for illustrative purposes only. Generally, a printing device  200  includes a door  210  covering an opening of the printing device  200 . A first print cartridge  220  and a second print cartridge  230  are designed to install within the printing device  200 . Both of the print cartridges  220 ,  230  are mounted on a carriage assembly (not shown) that provides linear horizontal movement across a print media.  
         [0030]    A service station, which is not shown in FIG. 2, attaches at an attachment point  240  at the side of the opening. The service station may be attached using a variety of techniques, such as a spur gear. When the service station is attached to the printing device  200  at the attachment point  240 , the service station is able to provide service station operations to the first print cartridge  220  and the second print cartridge  230 .  
         [0031]    III. Details of the Components and Operation  
         [0032]    [0032]FIG. 3 is an overview flow diagram of the general operation of the present invention. In general, the present invention begins with a print media operation, and is part of a cycle that completes that operation and momentarily reverse the motor direction, begins a service station operation, completes that operation and momentarily reverses the motor direction, and begins the cycle again.  
         [0033]    The cycle starts  300  and the print media is fed by the motor  136  to the printhead assembly  130 . The printhead assembly then operates a wide swath so that inks 1−n are ejected into the spittoon  302 . At this point, the motor  136  is engaged with the print media feed assembly  142  and disengaged from the service station drive assembly  148 . As explained in detail below, the motor  136  is then turned momentarily in the reverse direction  316  so as to engage the service station drive assembly  148  and disengage the print media feed assembly  142 . After the engagement of the service station drive assembly  148  and the disengagement of the print media feed assembly  142  the motor  136  is turned in the forward direction  340 .  
         [0034]    Once the service station drive assembly  148  is engaged With the motor  136  service station operations may be performed on the printhead assembly  130 . These service station operations include, for example, capping, wiping and priming operations. Once the service station assembly  166  has performed the desired servicing of the printhead assembly  130  the motor  136  is momentarily turned in the reverse direction  356 . This action disengages the service station drive assembly  148  and engages the print media feed assembly  142 . The motor  136  is then turned in the forward direction  380  and the print media is fed by the print media feed assembly  142  to the printhead assembly  130 .  
         [0035]    [0035]FIG. 4 shows a block diagram of an overall printing system incorporating the present invention. The printing system  100  of the present invention includes a printhead assembly  130 , an inks 1−n  118  and print media  142 . The printhead assembly  130  includes a controller  112 , heater elements  417 , ink chambers  418  with orifices or nozzles  420  fluidically coupled to associated ink channels  421 .  
         [0036]    During a printing operation, inks 1−n  118  through the ink channels  421  supply ink to an interior portion (such as an ink reservoir) of the printhead assembly  130 . The interior portion of the printhead assembly  130  provides ink to the ink chambers  418  for allowing ejection of ink through adjacent nozzles  420 . The printhead assembly  130  receives commands from a controller  112  to print ink and form a desired pattern for generating text and images on the print media  142 . Print quality of the desired pattern is dependent on the formation of ink droplets uncontaminated by such factors as dye enrichment or ink plugs.  
         [0037]    Ways to maintain print quality include the incorporation of a service station  166  to cap  172  and wipe  178  the printhead, and to prevent the development of an ink plug. The nozzles  420  can be cleared by ejecting ink into a spittoon  450  placed at a wider scan width. In a preferred embodiment of the current invention, nozzles would be cleared by ejecting inks 1−n  118  on spit strips  440  on available margins on the periphery of the print media  142 . The printhead assembly  130  traverses the carriage of the printer a set distance to print on the print media  142 , and a further set distance to eject inks 1−n  118  from nozzles not currently printing ink to the print media  142  on to the spit strips  440 . This action prevents the development of ink plugs on the nozzle array  420 . These spit strips  440  would be trimmed from the print media by the spit strip trimmer  442  during the feed print media  142 .  
         [0038]    In addition, the printhead  130  has been programmed to traverse a further distance to the spittoon  450  at the start of a printing operation and at specific moments during the printing operation. The controller  112  contains an analyzer  416  that receives information from the sensors  452  located in the spittoon  450 . By controlling the number of times inks are ejected into the spittoon, the amount of aerosol contamination in the printing system  100  is decreased. In an alternative embodiment, the spittoon  450  is not needed and not used, since the spit strips are used. As such, disposal of the ink in the spittoon would be avoided, which may be considered hazardous waste disposal by some regulatory governing bodies.  
         [0039]    [0039]FIG. 5 is a block diagram of the printhead assembly incorporating features of the present invention. The controller  112  contains the input output buffer  502 , the logic mapping system  516 , the format buffer  506 , temporary buffer  508 , and the printer sweep 1−n  510 . When data enters the system from the data input  430  it is held in the input/output buffer  502  of the controller  116  while the logic mapping system  516  analyzes the data.  
         [0040]    After the logic mapping system  516  has assigned pixel locations for the data these locations are transferred to the format buffer  506  for the formation of rasters. The data are then held in a temporary buffer  508  while the printer sweep 1−n  510  formats the data for the print cartridges. These data are relayed to the heater elements  417  which cause the heating of the ink chamber  418  and the ejection of ink from the nozzle array  420  to the print media  142 , the spit strip  440 , and as programmed, to the spittoon  450 . In the same time frame the printer sweep 1−n  510  communicates with the swath 1−n system  520  so that the width of the swath will match the data of the nozzle array  420 .  
         [0041]    Sensors  452  in the spittoon  450  transfer data to the analyzer  416 . Data from the analyzer  416  are integrated with data from the input/output buffer in the logic mapping system  516 . These data are incorporated in the subsequent formats as required.  
         [0042]    IV. Working Example  
         [0043]    [0043]FIG. 6 is a pictorial diagram illustrating the spit strips disposed on print media with an image and is shown for illustrative purposes only. Referring to FIG. 6 along with FIGS.  1 - 5 , print media  600 , which can be any suitable media, such as a standard 81/2″×11″ sheet of paper or a special continuous roll of photo paper, includes an image  605  that is printed on it. Spit strip  610 , preferably along the top margin, and spit strips  620 , preferably along the side margins, can be printed within the margins and outside the image  605 . The spit strip size could be any size suitable to keep the nozzles in working order and to prevent dye enrichment, while not wasting ink. In this example, spit strip  610  is approximately 0.125 inches wide and spit strips  620  are approximately 0.25 inches wide.  
         [0044]    In addition, preferably, the print media  600  is cropped to enable discarding of the spit strips  610  and  620 . Alternatively, the print media  600  can have perforated edges along the margins to allow removal of the spit strips  610  and  620 . It should be noted that FIG. 6 shows the spit strips  610  and  620  at the edge of the print media  600  for illustrative purposes only. Depending on how the margins are configured with the printer, the spit strips  620  can be printed anywhere suitable within the margins and not on the image  605 .  
         [0045]    The spit strips decrease the quantity of aerosol accumulation of ink on the printing system. Also, it purges, outside the image, a portion of the ink in the nozzles that have become dye enriched. This is advantageous because using the dye enriched ink on a portion of the image creates quality defects.  
         [0046]    The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Therefore, the foregoing description should not be taken as limiting the scope of the invention defined by the appended claims.  
         [0047]    The foregoing has described the principles, preferred embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. As an example, the above-described inventions can be used in conjunction with inkjet printers that are not of the thermal type, as well as inkjet printers that are of the thermal type. Thus, the above-described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.