Abstract:
In one example, a processor readable medium has instructions thereon that when executed cause a printer to: introduce an unsaturated printing fluid into a channel through which fluid may pass to a printhead; dispense unsaturated printing fluid with the printhead to remove air from the channel; and then introduce regular printing fluid into the channel; and dispense printing fluid with the printhead until regular printing fluid is dispensed from the printhead.

Description:
BACKGROUND 
       [0001]    In some inkjet printers, a substrate wide print bar is used to print on paper or other print substrates moved past the print bar. Inkjet print bars usually include multi-part flow structures with channels for ink to flow from the supply to a printhead or to multiple printheads. 
     
    
     
       DRAWINGS 
         [0002]      FIGS. 1 and 2  are block diagrams illustrating an inkjet printer implementing one example of a new air removal system. 
           [0003]      FIG. 3  is a block diagram illustrating an inkjet printer implementing another example of the new air removal system. 
           [0004]      FIG. 4  is a perspective view illustrating a printer and service module such as might be used in the air removal system shown in  FIG. 3 . 
           [0005]      FIGS. 5-8  are perspective views illustrating one example of a print bar such as might be used in the printer shown in  FIG. 4 . 
           [0006]      FIG. 9  is a flow diagram illustrating one example of a method for removing air from a printing fluid channel such as might be implemented with the air removal system shown in  FIGS. 1 and 2  or the air removal system shown in  FIG. 3 . 
           [0007]      FIG. 10  is a flow diagram illustrating one example for introducing unsaturated printing fluid into the flow channels in the method of  FIG. 9 . 
           [0008]      FIG. 11  is a flow diagram illustrating one example for introducing regular printing fluid into the flow channels in the method of  FIG. 9 . 
           [0009]      FIG. 12  is a flow diagram illustrating another example of a method for removing air from a printing fluid channel such as might be implemented with the air removal system shown in  FIGS. 1 and 2  or the air removal system shown in  FIG. 3   
       
    
    
       [0010]    The same part numbers designate the same or similar parts throughout the figures. 
       DESCRIPTION 
       [0011]    Too much air in the flow channels in an inkjet print bar can inhibit the flow of ink to the printheads, causing the printheads to perform poorly. A new technique has been developed to reduce the amount of air in the fluid flow channels in an inkjet print bar. In one example, unsaturated printing fluid is introduced into the print bar flow channels and dispensed from the printheads so that air is absorbed into the unsaturated printing fluid as it moves through the flow channels to the printheads. Once the desired quantify of air is removed from the flow channels, regular printing fluid is introduced into the flow channels and printing fluid dispensed from the printheads until the regular printing fluid reaches the printheads to begin normal printing. In one example, air removal programming resides on the printer controller to perform air removal using service cartridges (with unsaturated printing fluid) installed into the print bar in place of the regular printing fluid supply cartridges. In another example, air removal is performed at the direction of programming that resides at a service center using a service module that supplies unsaturated printing fluid to the print bar flow channels. 
         [0012]    Unlike printers that use replaceable, scanning printheads, substrate wide print bars are usually designed as a permanent part of the printer. Removing air from the flow channels in a substrate wide print bar not only helps improve print quality, but it also helps extend the useful life of the print bar and thus the printer too. Air removal may be performed before regular printing during the initial printer set-up to remove air that may have accumulated in the flow channels during storage and shipping. Air removal may be performed periodically throughout the life of the printer to remove air that can accumulate during use. Air may be removed using examples of the new technique without removing the print bar from the printer, thus saving time and minimizing the risk of damaging the print bar. 
         [0013]    Although examples are described with reference to a substrate wide print bar, examples may be implemented in other inkjet type dispensing devices. Accordingly, the examples described in this Description and shown in the Drawings illustrate but do not limit the disclosure, which is defined in the Claims following this Description. 
         [0014]    As used in this document, a “printhead” means that part of an inkjet printer or other inkjet type dispenser for dispensing a printing fluid, for example as drops or streams; a “print bar” means a usually elongated structure or device holding a single printhead or multiple printheads that remains stationary during printing; “printing fluid” means a fluid that may be dispensed from a printhead including, for example, ink and shipping fluid; “regular” printing fluid means printing fluid used for normal printing or other normal dispensing operations; and “unsaturated” printing fluid means a printing fluid that can absorb air as it passes through a flow channel in a print bar or other inkjet type dispensing device. While the air saturation level for “unsaturated” printing fluid may vary depending on the characteristics of the printing fluid and dispensing device, it is expected that an air saturation level less than 70% usually will be needed for effective air removal and that an air saturation level less than 50% usually will be desirable for faster air removal. Although regular printing fluid usually will be saturated printing fluid, an unsaturated printing fluid could also be used as the regular printing fluid. “Printhead” and “print bar” are not limited to printing with ink but also include inkjet type dispensing of other fluids and/or for uses other than printing. 
         [0015]      FIGS. 1 and 2  are block diagrams illustrating an inkjet printer  10  implementing one example of an air removal system  12 . Referring first to  FIG. 1 , printer  10  includes a print bar  14  spanning the width of a print substrate  16 , flow regulators  18  associated with print bar  14 , a substrate transport mechanism  20 , ink or other regular printing fluid supplies  22 , and a printer controller  24 . Print bar  14  includes printheads  26  for dispensing printing fluid on to a sheet or continuous web of paper or other print substrate  16 . Although five printheads  26  are shown, more or fewer printheads  26  may be used. Printheads  26  receive printing fluid through a typically complex flow path that includes channels  28  from printing fluid supplies  22  into and through flow regulators  16 , and channels  30  in print bar  14 . For example, each channel  28  might carry ink from a corresponding cyan, magenta, yellow and black (CMYK) ink supply  22  to a flow regulator  18  which delivers the ink to print bar  14  where each color ink is distributed to printheads  26  through channels  30 . While regulators  18  and channels  28  are shown separate from print bar  14 , one or both of regulators  18  and channels  28  could be integrated into print bar  14 . 
         [0016]    Controller  24  represents the processor(s) and associated memory(ies) and instructions, and the electronic circuitry and components needed to control the operative elements of printer  10 . In particular, controller  24  includes a processor readable medium (PRM)  32  with instructions  34  for controlling the removal of air from channels  28  and  30 . Control functions for many printers, particularly printers for small business and personal use, are implemented in application specific integrated circuits (ASICs). Accordingly, some or all of the functionality of controller  24  in printer  10 , including PRM  32  and air removal instructions  34 , may be implemented in an ASIC. However, other suitable implementations for PRM  32  and instructions  34  are possible. 
         [0017]    Referring now to  FIG. 2 , for air removal each regular printing fluid supply  20  is replaced with a service cartridge  36  containing unsaturated printing fluid. Air removal system  12  includes service cartridges  36  and air removal instructions  34  on a controller PRM  32 . In one example, the unsaturated printing fluid is shipping fluid. In another example, the unsaturated printing fluid is ink. Once the air removal is complete, as described below with reference to the flow diagrams of  FIGS. 9-12 , service cartridges  36  are removed and regular printing fluid supplies  22  are installed for normal printing. 
         [0018]      FIG. 3  is a block diagram illustrating an inkjet printer  10  implementing another example of an air removal system  12 . In this example, and referring to  FIG. 3 , processor readable medium  32  with air removal instructions  34  resides at a service center  38  that is operatively connected to printer  10  for air removal. Service center  38  also includes a service module  40  with unsaturated printing fluid supplies (UPF)  36 . Air removal system  12  in  FIG. 3  includes service module  40  with UPF supplies  36  and instructions  34  on a service center PRM  32 . For air removal, each unsaturated printing fluid supply  36  is connected to a corresponding flow channel  28  through adapters  42 . Although four adapters  42  are shown in the example of  FIG. 3 , each corresponding to one of the supplies  36 , other adapter configurations are possible. For example, a single adapter with multiple ports to connect supplies  36  to channels  28  could be used. 
         [0019]    Service cartridges  36  in  FIG. 2  and UPF supplies  36  in  FIG. 3  represent any suitable source of unsaturated printing fluid. For example, unsaturated printing fluid may be introduced into channels  28  directly from containers specially designed to maintain unsaturated printing fluid. For another example, an in-line degasser (degassers  53  in  FIG. 8 ) may be interposed between channels  28  and containers of saturated printing fluid to deliver unsaturated printing fluid to channels  28 . Also, air removal instructions  34  need not reside solely on a processor readable medium  32  on printer controller  24  or at a service center  38  (or other site or device separate from printer  10 ). Similarly, one processor or multiple processors on controller  24  or separate from controller  24  (or both) may be used to execute instructions  34 . Accordingly, suitable configurations other than those shown for storing and executing air removal instructions  34  are possible. 
         [0020]      FIG. 4  is a perspective view illustrating a printer  10  and service module  40  such as might be used in the air removal system  12  shown in  FIG. 3 .  FIG. 5  is a top view of one example of a print bar  14  such as might be used in the printer  10  shown in  FIG. 3 .  FIG. 6  is an exploded view of print bar  14  in  FIG. 5 . Regular printing fluid supplies  22  are installed in print bar  14  for normal printing operations in  FIGS. 5 and 6 .  FIG. 7  is a bottom view of print bar  14  showing one example arrangement for printheads  26  and  FIG. 8  is an exploded top view of print bar  14  with an air removal adapter  42  installed in place of the regular printing fluid supplies. 
         [0021]    Referring first to  FIGS. 4-6 , for normal printing operations print bar  14  in printer  10  includes regular printing fluid supply cartridges  22 , for example to supply cyan, magenta, yellow and black (CMYK) ink. Supply cartridges  22  are held in a support  48  and connected to printing fluid ports  50  and air ports  52 . Printing fluid flows from supply cartridges  22  to flow regulators  18  through ports  50  and channels  28 . In this example, as shown in  FIGS. 5 and 6 , flow regulators  18  are housed on top of print bar  14  in a housing  54  and cartridge support  48  is mounted to housing  54 . 
         [0022]    Referring now to  FIGS. 4 and 8 , for air removal regular printing fluid supply cartridges  22  are removed and a service module  40  with unsaturated printing fluid supplies  36  is connected to printing fluid ports  50  through adapter  42  and tubes  44 . In this example, the unsaturated printing fluid is ink the same color (CMYK) as the ink used for normal printing and system  12  includes an in-line degasser  53  for each color. Once air removal is complete, adapter  42  is disconnected and regular printing fluid supplies  22  installed for normal printing. 
         [0023]      FIG. 9  is a flow diagram illustrating one example of a method  100  for removing air from a printing fluid channel such as might be implemented in a system  12  shown in  FIGS. 1 and 2  or a system  12  shown in  FIG. 3 . The method of  FIG. 9  may be performed, for example, at the direction of controller  24  executing air removal instructions  34 . Air removal instructions  34  may be embodied in a local PRM  32  residing on controller  24  as shown in  FIGS. 1 and 2 , or in a PRM  32  separate from controller  24 , for example at a service center  38  shown in  FIG. 3 . Referring to  FIG. 9 , unsaturated printing fluid is introduced into flow channels  28  and  30  (block  102 ) and dispensed with some or all printheads  26  to remove air from the channels (block  104 ). Once the desired amount of air is removed, regular printing fluid is introduced into channels  28  and  30  (block  106 ). Where the unsaturated printing fluid is usable for normal printing, it may not be necessary or desirable to introduce the regular printing fluid into print bar channels  30  as part of the air removal operation shown in  FIG. 9 . 
         [0024]    Referring again to  FIGS. 2 and 3 , as printing fluid is dispensed from printheads  26 , the unsaturated printing fluid moving through channels  28  and  30  will absorb air and carry it to printheads  26  where it is discharged from print bar  14 . As the unsaturated printing fluid absorbs air on its way to printheads  26 , it may become saturated with air. Thus, the character of the unsaturated printing fluid may change from unsaturated to saturated at times during the air removal operation as it moves to printheads  26 . The step of dispensing “unsaturated” printing fluid at block  104  in  FIG. 9  includes any such change in character. That is to say, dispensing “unsaturated” printing fluid includes dispensing saturated printing fluid that originated upstream from the printheads as unsaturated printing fluid. 
         [0025]      FIG. 10  is a flow diagram illustrating one example for introducing unsaturated printing fluid into flow channels  28  and  30  at block  102  in  FIG. 9 . Referring to  FIG. 10 , regular printing fluid supplies  22  in  FIG. 1  are disconnected from print bar  14  (block  108 ) and unsaturated printing fluid supplies  36  are connected to print bar  14  as shown in  FIG. 2  (block  110 ). The unsaturated printing fluid supplies  36  are automatically detected by controller  24  (block  112 ) and then printing fluid is dispensed from some of all of printheads  26  to move unsaturated printing fluid into channels  28  and  30  (block  114 ). The disconnecting and connecting actions at blocks  108  and  110  are user actions while the detecting and dispensing actions at blocks  112  and  114  are printer actions undertaken at the direction of controller  24 . Alternatively, the step of automatically detecting the unsaturated printing fluid supplies to initiate dispensing may be omitted and, instead, the user can manually initiate dispensing after connecting the unsaturated printing fluid supplies by entering a command at the printer control panel  46  ( FIG. 4 ). Also, where the air removal operation is performed before the regular printing fluid supplies have been connected, during initial printer setup for example, then disconnecting the regular printing fluid supplies at block  108  is omitted. 
         [0026]      FIG. 11  is a flow diagram illustrating one example for introducing regular printing fluid into flow channels  28  at block  106  in  FIG. 9 . Referring to  FIG. 11 , unsaturated printing fluid supplies  36  in  FIG. 2  or  FIG. 3  are disconnected from print bar  14  (block  116 ) and regular printing fluid supplies  22  are connected to print bar  14  as shown in  FIG. 1  (block  118 ). The regular printing fluid supplies  22  are automatically detected by controller  24  (block  120 ) and then printing fluid is dispensed from some of all of printheads  26  to move regular printing fluid into channels  28  and  30  (block  122 ). The disconnecting and connecting actions at blocks  116  and  118  are user actions while the detecting and dispensing actions at blocks  120  and  122  are printer actions undertaken at the direction of controller  24 . Alternatively, the step of automatically detecting the regular printing fluid supplies to initiate dispensing may be omitted and, instead, the user can manually initiate dispensing after connecting the regular printing supplies by entering a command at the printer control panel  46  ( FIG. 4 ). 
         [0027]    Most ink cartridges and other inkjet printing fluid supplies now include an electronic chip that identifies the supply and stores information about the supply. Electrical contacts on the chip connect to mating contacts on the printer to allow the printer controller to automatically detect the presence of a printing fluid supply, identify the supply, and obtain information about the supply. A similar electronic chip on the service cartridges  36  and the adapter(s)  42  may be used to allow the printer controller to automatically detect the presence of a service cartridge/adapter, to identify the cartridge/adapter and to obtain information about the unsaturated printing fluid used for air removal. 
         [0028]    The air removal operation continues until a threshold amount of air is removed from the channels. While it is expected that substantially all of the air usually will be removed from the channels, a lower threshold might also be used. “Substantially all” in this context means all of the air that can be absorbed into the unsaturated printing fluid as the printing fluid moves through the flow channels. Ideally, the unsaturated printing fluid will absorb 100% of the air in the flow channels, but in practice the actual amount of air absorbed may be lower than 100%. In one example, the amount of air removed is determined by measuring the concentration of air in the printing fluid dispensed from the printheads. An air concentration below the saturation level indicates that substantially all air has been removed from the flow channels. In another example, the air removal process continues until a predetermined volume of unsaturated printing fluid corresponding to the desired threshold of air removal is dispensed from the printheads. Also, introducing unsaturated printing fluid rapidly into the flow channels to quickly displace a significant volume of printing fluid already in the channels can help improve the effectiveness of the air removal process. Air tends to accumulate downstream, closer to the dispensing nozzles. Introducing unsaturated printing fluid quickly for about one-half the total volume of the flow channels helps get unsaturated printing fluid to the air faster and then slowing the flow for the remainder of the air removal process allows time for the printing fluid to absorb the air. 
         [0029]      FIG. 12  is a flow diagram illustrating one example of a “fast/slow” air removal method  124  such as might be implemented in a system  12  shown in  FIGS. 1 and 2  or a system  12  shown in  FIG. 3 . The method of  FIG. 12  may be performed, for example, at the direction of controller  24  executing air removal instructions  34 . Referring to  FIG. 12 , unsaturated printing fluid is introduced into the flow channel or into multiple flow channels by dispensing printing fluid from a printhead or from multiple printheads at a first, faster rate for about 50% of the total volume of the flow channel(s) (block  126 ). Then, printing fluid is dispensed from the printhead(s) at a second, slower rate to remove air from the channel(s) to the desired threshold (block  128 ). Once the desired threshold is reached, regular printing fluid may be introduced into the flow channel(s) to begin or resume normal printing operations. 
         [0030]    “A” and “an” as used in the Claims means one or more. 
         [0031]    The examples shown in the figures and described above illustrate but do not limit the disclosure, which is defined in the following Claims. Other forms, details, and examples may be made and implemented. Therefore, the foregoing description should not be construed to limit the scope of the Claims.