Cleaning of fluid ejection assembly

A method includes applying a nominal back pressure to a fluid ejection assembly and nozzles to form a first amount of back pressure therein by a back pressure regulator. The method also includes applying a first pressure to lower the first amount of back pressure within the fluid ejection assembly and the nozzles to form a second amount of back pressure therein by a pressurization module in response to an activation of a cleaning operation. The method also includes moving at least one of the fluid ejection assembly and a wicking member against each other to perform the cleaning operation. The wicking member moves relative to the fluid ejection assembly against and across the nozzle surface to transfer fluid residue from at least one of the nozzle surface and the nozzles to a portion of the wicking member to form a used wicking member portion.

BACKGROUND

Printing apparatuses may include a fluid ejection assembly to form an image on media. The fluid ejection assembly may include a nozzle surface having a plurality of nozzles. The fluid ejection assembly may eject printing fluid from the nozzles and onto the media.

DETAILED DESCRIPTION

Printing apparatuses may include a fluid ejection assembly to form an image on media and a back pressure regulator to provide a nominal back pressure to reduce unwanted drooling of printing fluid and occurrences of depriming events from the fluid ejection assembly. The fluid ejection assembly, for example, may include an inkjet printhead including a nozzle surface having a plurality of nozzles. The back pressure regulator, for example, may include porous foam, and the like. The fluid ejection assembly may selectively eject printing fluid from the nozzles and onto media. For example, in a thermal inkjet printhead, a bubble may be generated by heat therein and subsequently collapse resulting in a printing fluid drop being ejected from a respective nozzle. Fluid residue may accumulate at the nozzle surface and nozzles. Periodically, a wicking member such as a web wipe may be repeatedly used to rub against the fluid ejection assembly and clean the nozzle surface and nozzles during a cleaning operation.

For example, when a web wipe is performed, a meniscus pressure at the respective nozzles may be overcome by a capillary draw provided by the wicking member to the nozzles for printing fluid to flow from the nozzles to the wicking member. As the wicking member is reused, the capillary draw may be decreased in which less printing fluid may be drawn out from the nozzles with each successive reuse. Consequently, the nominal back pressure and the tendency of the reused wicking member to push air into the nozzles once the respective menisci are broken may result in air ingestion into the nozzles. That is, air trapped between the wicking member and nozzle surface may be pushed into the nozzles due to reduced permeability of the used wicking member and also pulled into the nozzles due to the application of the nominal back pressure to the fluid ejection assembly and the nozzles. Such air and/or fluid residue may be ingested into the nozzles during a cleaning operation and impede proper printing fluid drop ejection therefrom. Thus, image quality may be decreased and/or fluid ejection assembly damage may result.

In examples, a method of cleaning a fluid ejection assembly including a nozzle surface having nozzles to eject printing fluid therefrom includes, amongst other things, applying a nominal back pressure to the fluid ejection assembly and the nozzles to form a first amount of back pressure therein by a back pressure regulator. The method also includes applying a first pressure to lower the first amount of back pressure within the fluid ejection assembly and the nozzles to form a second amount of back pressure therein by a pressurization module in response to an activation of a cleaning operation. The method also includes moving at least one of the fluid ejection assembly and a wicking member of a cleaning module against each other to perform the cleaning operation.

During the cleaning operation, a wicking member moves relative to the fluid ejection assembly against and across the nozzle surface to transfer fluid residue from at least one of the nozzle surface and the nozzles to a portion of the wicking member to form a used wicking member portion. Periodically, a wicking member such as a web wipe may be repeatedly used to rub against the fluid ejection assembly to clean the nozzle surface and nozzles during a cleaning operation. Such a reduction of pressure for a cleaning operation may reduce the tendency of air to be ingested into the nozzles and prolong reuse of the wicking member. Thus, image quality degradation and fluid ejection assembly damage may be reduced.

FIG. 1is a block diagram illustrating a printing apparatus according to an example. Referring toFIG. 1, in some examples, a printing apparatus100includes a fluid ejection assembly10, a back pressure regulator16, a cleaning module11, and a pressurization module12. The fluid ejection assembly10may include a nozzle surface13having a plurality of nozzles14. The fluid ejection assembly10may eject printing fluid from the nozzles14. In some examples, the fluid ejection assembly10may include a printhead, plurality of printhead modules, a printbar, and/or a printhead assembly, and the like. For example, in a thermal inkjet printhead, a bubble may be generated by heat therein and subsequently collapse resulting in a printing fluid drop being ejected from a respective nozzle14.

Referring toFIG. 1, in some examples, the back pressure regulator16may provide a nominal back pressure to the fluid ejection assembly10and the nozzles14to form a first amount of back pressure therein. In some examples, the back pressure regulator16may be disposed outside and/or inside the fluid ejection assembly10. For example, the back pressure regulator16may be disposed in a printing fluid supply in fluid communication with the fluid ejection assembly10. In some examples, the back pressure regulator16may include a porous foam member, and the like.

Referring toFIG. 1, in some examples, the cleaning module11may selectively move a wicking member25(FIGS. 2A and 3) against the nozzle surface13to remove fluid residue from at least one of the nozzle surface13and the nozzles14thereof during a cleaning operation. For example, the cleaning module11may be repositioned toward the fluid ejection assembly10and move the wicking member25against the nozzle surface13during a cleaning operation. Additionally, in some examples, the cleaning module11may be repositioned away from the fluid ejection assembly10in which the wicking member25may be moved away from the nozzle surface13in response to completion of a cleaning operation. In some examples, the cleaning module11may be repositioned by a motor, and/or mechanical members, and the like.

Referring toFIG. 1, in some examples, the pressurization module12may apply pressure to the fluid ejection assembly10and the nozzles14. The pressurization module12may apply a first pressure to lower the first amount of back pressure within the fluid ejection assembly10and the nozzles14to form a second amount of back pressure therein in response to an activation of the cleaning operation. Thus, a back pressure state may exist during the cleaning operation and after completion of the cleaning operation. The back pressure state, for example, is a state in which the net pressure within the fluid ejection assembly10is negative. In some examples, the first pressure may correspond to a positive amount of pressure provided by the pressurization module12to be added to the second amount of back pressure within the fluid ejection assembly10resulting in a net back pressure being less negative (e.g., decrease in back pressure).

That is, the amount of pull on menisci of the printing fluid in the nozzles14into the fluid ejection assembly10will be decreased by application of the first pressure by the pressurization module12. In some examples, the nominal back pressure and the first amount of back pressure may be about −9 inches H20. Also, in some examples, the first pressure may be about 7 inches H20. Consequently, in some examples, the second amount of back pressure may be about −2 inches H2O and formed in response to an activation of the cleaning operation. Consequently, a tendency of ingestion of air and/or fluid residue into the nozzles14when the wicking member25is moved against the nozzle surface13may be reduced.

FIGS. 2A and 2Bare schematic views illustrating a printing apparatus in a cleaning state and a non-cleaning state, respectively, according to examples.FIG. 3is a schematic view illustrating the printing apparatus ofFIG. 2Ain a cleaning state according to an example. Referring toFIGS. 2A-3, in some examples, the printing apparatus200may include the fluid ejection assembly10, the back pressure regulator16, the cleaning module11, and the pressurization module12as previously described with respect to the printing apparatus100ofFIG. 1.

As illustrated inFIG. 2A, the cleaning module11may selectively move the wicking member25against the nozzle surface13to remove fluid residue from at least one of the nozzle surface13and the nozzles14thereof during a cleaning operation. For example, in a cleaning state, the cleaning module11may be repositioned toward the fluid ejection assembly10and move the wicking member25in contact with the nozzle surface13. Alternatively, in response to completion of the cleaning state such as in a non-cleaning state, the cleaning module11may be repositioned away from the fluid ejection assembly10and move the wicking member25out of contact with the nozzle surface13as illustrated inFIG. 2B.

Referring toFIGS. 2A-3, in some examples, the cleaning module11may include a wicking member25, at least one cleaner transport member27, and a housing21. The wicking member25may include a web wipe having sufficient permeability to absorb fluid residue. At least one cleaner transport member27may move the wicking member25against and across the nozzle surface13to remove fluid residue therefrom. In some examples, the cleaning module11may include a plurality of cleaner transport members27such as cylindrical rollers to guide the wicking member25thereabout. One of the rollers, for example, may be a drive roller to move the wicking member25. For example, the wicking member25may be arranged in an endless loop and move in a web transport direction d, about the cleaner transport members27, and across the nozzle surface13and nozzles14.

In some examples, the housing21may selectively move toward the fluid ejection assembly10to perform the cleaning operation and away from the fluid ejection assembly10in response to completion of the cleaning operation. The housing21may be coupled to at least one cleaner transport member27. During the cleaning operation, the wicking member25may attract fluid residue from at least one of the nozzle surface13and the nozzles14to a portion of the wicking member25to form a used wicking member portion35. The cleaning module11may move the used wicking member portion35against and across the nozzle surface13to attract fluid residue from at least one of the nozzle surface13and the nozzles14thereto during a subsequent cleaning operation.

Referring toFIGS. 2A-3, in some examples, the pressurization module12may apply pressure to the fluid ejection assembly10and the nozzles14. As previously described, the pressurization module12may apply a first pressure to lower the first amount of back pressure within the fluid ejection assembly10and the nozzles14to form a second amount of back pressure therein in response to an activation of the cleaning operation. Additionally, in some examples, the pressurization module12may be configured to apply a second pressure that is less than the first pressure to increase the second amount of back pressure therein to form a third amount of back pressure therein in response to a completion of the cleaning operation.

In some examples, the second pressure may correspond to a negative amount of pressure provided by the pressurization module12to be added to the second amount of back pressure within the fluid ejection assembly10to form the third amount of back pressure. That is, the third amount of back pressure may correspond to a net back pressure being more negative (e.g., increase in back pressure) than the second amount of back pressure. In some examples, the second amount of back pressure may be about −2 inches H2O. Also, in some examples, the second pressure may be about −7 inches H2O. Consequently, in some examples, the third amount of back pressure may be about −9 inches H20 and formed in response to a completion of the cleaning operation. In some examples, the first amount of back pressure and the third amount of back pressure may be substantially the same.

FIG. 4is a schematic view illustrating a pressurization module and a fluid ejection assembly of the printing apparatus ofFIG. 2Baccording to an example. Referring toFIG. 4, in some examples, the pressurization module12of the printing apparatus200may include an inflatable bag42, a resilient member43, an air movement unit44, and a valve45. The pressurization module12may be in fluid communication with the fluid ejection assembly10through a fluid channel41there between. The resilient member43may interact with the inflatable bag42, for example, in an enclosed volume47of the printing fluid48and/or air. In some examples, the enclosed volume47may be in a form of a printing fluid supply.

The resilient member43, for example, may surround the inflatable bag42and apply a force fron the inflatable bag42and the surrounding fluid. In some examples, the force may be directly proportional to an amount of inflation of the inflatable bag42. As the inflatable bag42inflates, the pulling tendency of the resilient member43may lessen and the back pressure may be reduced. Also, the inflatable bag42may apply a force fbto the resilient member43based on its inflation state. In some examples, the resilient member43may include a spring, and the like. In some examples, the air movement unit44may selectively provide air to inflate the inflatable bag42. In some examples, the air movement unit44may include a pump, and the like. The valve45may remove the air from and deflate the inflatable bag42to its nominal inflation level. For example, the valve45may direct air from the inflatable bag42to outside the printing apparatus, for example, through a vent.

Referring toFIG. 4, in some examples, the pressurization module12may apply pressure to the fluid ejection assembly10and the nozzles14. That is, the inflatable bag42may inflate to apply the first pressure to lower the first amount of back pressure within the fluid ejection assembly10and the nozzles14to form the second amount of back pressure therein in response to the activation of the cleaning operation. For example, the air movement unit44may provide steady air flow to the inflatable bag42and through the valve45which provides a controlled air flow resistance to limit bag inflation to an equilibrium state and thus a steady amount of applied pressure. Additionally, the inflatable bag42may deflate by either slowing or stopping the motor to apply a second pressure that is less than the first pressure to increase the second amount of back pressure within the fluid ejection assembly10and the nozzles14to form a third amount of back pressure therein in response to the completion of the cleaning operation. In some examples, the valve45may direct air to outside the printing apparatus in order to control air flow resistance during inflation or allow air to escape during deflation of the inflatable bag42.

FIG. 5is a block diagram illustrating a printing system according to an example. Referring toFIG. 5, in some examples, a printing system500includes the fluid ejection assembly10, the back pressure regulator16, the cleaning module11, and the pressurization module12as previously described with respect to the printing apparatuses100and200ofFIGS. 1-4. Referring toFIG. 5, in some examples, the fluid ejection assembly10may include a nozzle surface13having a plurality of nozzles14. The fluid ejection assembly10may eject printing fluid from the nozzles14. The back pressure regulator16may provide a nominal back pressure to the fluid ejection assembly10and the nozzles14to form a first amount of back pressure therein.

Referring toFIG. 5, in some examples, the cleaning module11may include a wicking member25, and cleaner transport members27. The cleaner transport members27may move the wicking member25against and across the nozzle surface13to attract fluid residue from at least one of the nozzle surface13and the nozzles14to a portion of the wicking member25to form a used wicker member portion35during a cleaning operation. The cleaning module11may move the used wicking member portion35, for example, between cleaner transport members27against and across the nozzle surface13for a subsequent cleaning operation.

Referring toFIG. 5, in some examples, the pressurization module12may apply an amount of pressure to the fluid ejection assembly10and the nozzles14. The pressurization module12may include an inflatable bag42, and a resilient member43as previously described with respect to the printing apparatus200ofFIG. 4. The inflatable bag42may inflate and interact with the resilient member43to apply a first pressure to lower the first amount of back pressure within the fluid ejection assembly10and the nozzles14to form a second amount of back pressure therein in response to the activation of the cleaning operation. In some examples, the inflatable bag42may deflate to apply the second pressure that is less than the first pressure to increase the second amount of back pressure within the fluid ejection assembly10and the nozzles14to form the third amount of back pressure therein in response to the completion of the cleaning operation. In some examples, the pressurization module12may also include an air movement unit44and a valve45as previously described with respect to the printing apparatus200ofFIG. 4.

FIG. 6is a flowchart illustrating a method of cleaning a fluid ejection assembly including a nozzle surface having nozzles to eject printing fluid therefrom according to an example. In block S610, a nominal back pressure is applied to the fluid ejection assembly and the nozzles by a back pressure regulator to form a first amount of back pressure therein. In block S612, a first pressure to lower the first amount of back pressure within the fluid ejection assembly and the nozzles to form a second amount of back pressure therein is applied by a pressurization module in response to an activation of a cleaning operation. For example, an inflatable bag of the pressurization module may inflate to apply the first pressure to lower the first amount of back pressure within the fluid ejection assembly and the nozzles and to form the second amount of back pressure therein in response to the activation of the cleaning operation.

In block S614, at least one of the fluid ejection assembly and a wicking member of a cleaning module is moved against each other to perform the cleaning operation. Additionally, a wicking member moves relative to the fluid ejection assembly against and across the nozzle surface to transfer fluid residue from at least one of the nozzle surface and the nozzles to a portion of the wicking member to form a used wicking member portion. For example, the wicking member of the cleaning module may be moved against and across the nozzle surface to perform the cleaning operation to transfer the fluid residue from at least one of the nozzle surface and the nozzles to the portion of the wicking member to form the used wicking member portion.

In some examples, the method may also include applying a second pressure that is less than a first pressure to increase the second back pressure within the fluid ejection assembly and the nozzles to form the third amount of back pressure therein in response to a completion of the cleaning operation. For example, the inflatable bag of the pressurization module may deflate to apply the second pressure to increase the second amount of back pressure within the fluid ejection assembly and the nozzles to form the third amount of back pressure therein in response to the completion of the cleaning operation. In some examples, the first amount of back pressure and the third amount of back pressure may be substantially equal.

In some examples, the method may include applying the first pressure to lower the third amount of back pressure within the fluid ejection assembly and the nozzles to form a fourth amount of back pressure therein by the pressurization module in response to an activation of a subsequent cleaning operation. In some examples, the second amount of back pressure and the fourth amount of back pressure may be substantially equal. Additionally, the method may include moving the used wicking member portion against and across the nozzle surface of the fluid ejection assembly by the cleaning module to transfer fluid residue from the nozzle surface and the nozzles to the used wicking member portion to perform the subsequent cleaning operation.

It is to be understood that the flowchart ofFIG. 6illustrates architecture, functionality, and/or operation of examples of the present disclosure. If embodied in software, each block may represent a module, segment, or portion of code that includes one or more executable instructions to implement the specified logical function(s). If embodied in hardware, each block may represent a circuit or a number of interconnected circuits to implement the specified logical function(s). Although the flowchart ofFIG. 6illustrates a specific order of execution, the order of execution may differ from that which is depicted. For example, the order of execution of two or more blocks may be rearranged relative to the order illustrated. Also, two or more blocks illustrated in succession inFIG. 6may be executed concurrently or with partial concurrence. All such variations are within the scope of the present disclosure.

The present disclosure has been described using non-limiting detailed descriptions of examples thereof that are not intended to limit the scope of the general inventive concept. It should be understood that features and/or operations described with respect to one example may be used with other examples and that not all examples have all of the features and/or operations illustrated in a particular figure or described with respect to one of the examples. Variations of examples described will occur to persons of the art. Furthermore, the terms “comprise,” “include,” “have” and their conjugates, shall mean, when used in the disclosure and/or claims, “including but not necessarily limited to.”

It is noted that some of the above described examples may include structure, acts or details of structures and acts that may not be essential to the general inventive concept and which are described for illustrative purposes. Structure and acts described herein are replaceable by equivalents, which perform the same function, even if the structure or acts are different, as known in the art. Therefore, the scope of the general inventive concept is limited only by the elements and limitations as used in the claims.