Patent Application
20130286090
This disclosure relates generally to inkjet printers that eject ink to form images on print media, and, more particularly, to components in inkjet printers that can accumulate ink build-up during printing operations.
In general, inkjet printers include at least one printhead that ejects drops of liquid ink onto an image receiving surface to produce ink images on recording media. A phase change inkjet printer employs phase change inks that are in the solid phase at ambient temperature, but transition to a liquid phase at an elevated temperature. A mounted printhead ejects drops of the melted ink to form an ink image on an image receiving surface. The image receiving surface can be the surface of print media or an image receiving member, such as a rotating drum or endless belt. Ink images formed on an image receiving member are later transferred to print media. Once the ejected ink is onto the media or image receiving member, the ink droplets quickly solidify to form an image.
The media on which ink images are produced can be supplied in sheet or web form. A media sheet printer typically includes a supply drawer that houses a stack of media sheets. A feeder removes a sheet of media from the supply and directs the sheet along a feed path past a printhead so the printhead ejects ink directly onto the sheet. In offset sheet printers, a media sheet travels along the feed path to a nip formed between the rotating imaging member onto which the ink image was formed and a transfix roller. The pressure and heat in the nip transfer the ink image from the imaging member to the media. In a web printer, a continuous supply of media, typically provided in a media roll, is entrained onto rollers that are driven by motors. The motors and rollers pull the web from the supply roll through the printer to a take-up roll. As the media web passes through a print zone opposite the printhead or heads of the printer, the printheads eject ink onto the web. Along the feed path, tension bars or other rollers remove slack from the web so the web remains taut without breaking.
An inkjet printer conducts various maintenance operations to ensure that the ink ejectors in each printhead operate efficiently. A cleaning operation is one such maintenance operation. The cleaning process removes particles or other contaminants that may interfere with printing operations from the printhead and may unclog solidified ink or contaminants from inkjet ejectors. During a cleaning operation, the printheads purge ink through some or all of the ink ejectors in the printhead. The purged ink flows through the ejectors and down the front face of the printheads, where the ink drips into an ink receptacle. To control the flow of ink down the face of each printhead, some printheads include a drip bib. The drip bib has a shape that directs liquid ink toward the ink receptacle. The lower edge of the drip bib tapers to one or more channels or points where ink collects prior to dripping into the receptacle. In some printers, a wiper engages the front face of the printhead and wipes excess purged ink in a downward direction toward the drip bib to remove excess purged ink.
While the cleaning process removes most purged ink from the face of the printhead and the drip bib, small amounts of residual ink may accumulate on both the printhead face and the drip bib over time. These small amounts of ink can be produced by printing operations and by printhead maintenance operation. Ink that accumulates on the printhead face plate promotes “drooling” of ink through one or more inkjet nozzles due to capillary attraction between ink on the face of the printhead and ink within a pressure chamber in nearby inkjets. The drooled ink can form spurious marks on the image receiving surface and can interfere with the operation of inkjets in the printhead. Ink that adheres to the drip bib collects near a lower edge of the drip bib and can release from the drip bib after completion of the maintenance operation. In addition to forming spurious marks on the print medium, phase-change inks on drip bibs can cool and solidify prior to being released from the drip bib. The moving print media can carry the solidified ink past the printhead where the solidified ink can strike the printhead face with possibly adverse consequences to the printhead.
Existing printhead faces and drip bibs are often coated with a low surface energy material, such as polytetrafluoroethylene, which is sold commercially as Teflon®. The low surface energy material is also referred to as an “anti-wetting” material that resists the adhesion of liquid ink to the printhead or the drip bib. The low surface energy material is applied during the manufacture of the printhead face and drip bib. After prolonged use in a printer, however, the low surface energy coating can gradually wear away. For example, repeated contact with the print medium during operation can erode Teflon from the printhead face and the drip bib. Additionally, repeated contact with wiper blades and other printhead maintenance unit components can erode the low surface energy material. Over time, the printhead and drip bib may begin to accumulate larger amounts of excess ink, which can artificially shorten the operational lifetime of the printhead.
In one embodiment, a method for performing printhead maintenance has been developed that reduces the adhesion of ink to a printhead. The method includes applying a low surface energy material to a face of a printhead during a printhead maintenance operation.
In another embodiment, a method for performing printhead maintenance has been developed that reduces the adhesion of ink to a drip bib. The method includes applying a low surface energy material to a surface of a drip bib located below a face of a printhead during a printhead maintenance operation.
In another embodiment, there is presented a method for performing maintenance on a printhead unit in a printer comprising: applying a low surface energy material to a face plate of a printhead during a printhead operation.
In yet another embodiment, there is presented a method for performing maintenance on a printhead unit in a printer comprising: wiping a face plate of a printhead to remove ink from the face plate of the printhead; and applying a low surface energy material to the face plate of the printhead, wherein the low surface energy material reduces or prevents printhead drooling.
In an alternative embodiments, there is presented a method for performing maintenance on a printhead unit in a printer comprising: wiping a face plate of a printhead to remove ink from a face plate of a printhead; applying a low surface energy material to the face plate of the printhead during a printhead maintenance operation, wherein the low surface energy material is applied in a layer having a thickness of greater than 0 nm to about 100 nanometers.
For a general understanding of the environment for the system and method disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein the termn “printer” refers to any device that is configured to eject a marking agent upon an image receiving surface and include photocopiers, facsimile machines, multifunction devices, as well as direct and indirect inkjet printers. An image receiving surface refers to any surface that receives ink drops, such as an imaging drum, imaging belt, or various print media including paper.
As used herein, the term “low surface energy material” refers to a material that tends to prevent a liquid from wetting, and consequently adhering to, a surface. For example, liquid ink can adhere to the surface of printhead face plates or drip bibs. A coating of a low surface energy material, however, resists the adhesion of the ink to the surface. Instead, the liquid ink contracts into one or more droplets due to the inherent surface tension of the ink and the drops slide down the surface of the printhead or drip bib under the force of gravity. Eventually the ink flows to a lower edge of the printhead, such as to a lower edge of the drip bib, and the liquid ink detaches from the printhead for collection in a waste ink receptacle. One example of a low surface energy material is silicone oil, which is also referred to as a silicone fluid. Various forms of silicone oil are sold commercially and can include different additives. In particular, amino modified silicone oils include alkyl amino additives. Alkyl amino additives promote bonding between the silicone oil and metal surfaces such as metal surfaces of the printhead face and drip bib. In embodiments, the additives are present in the silicone oil in an amount of from about 0.02 percent to about 0.30 percent, or from about 0.05 percent to about 0.10 percent, or from about 0.20 percent to about 0.30 percent by weight of the total weight of the silicone oil. One example of a silicone oil is Xerox product part number 008R13115, labeled as “Spreader Agent,” and sold by the Xerox Corporation of Norwalk, Conn. A reference to silicone oil in this document includes silicone oils with or without additives. Silicone oils are described as non-limiting examples of low surface energy materials, but those having skill in the art recognize that other appropriate materials with low surface energy properties can be used with the processes described below.
The low surface energy material can be applied to the printhead face 408 and drip bib 412 manually or automatically during a printhead maintenance process. In embodiments, the low surface energy material is applied in a layer having a thickness of greater than 0 nm to about 100 nm, or greater than 0 nm to about 50 nm, or from about 2 nm to about 10 nm.
Process 300 begins when ink is purged through the inkjet nozzles in the inkjet nozzle plate 410 (block 304). In one embodiment, pressurized air is applied to an ink reservoir that supplies ink to the inkjet nozzles to urge ink through the inkjets and out of the nozzles. The energy of this released ink is less than that of ejected ink drops so the purged ink subsequently flows down the surface of the printhead face 408 and the drip bib 412. Most of the purged ink drips from the drip bib 412 and enters an ink collection receptacle (not shown) that is positioned below the printhead assembly 400.
After the printhead purges ink, the printhead maintenance unit can optionally wipe the printhead face 408 (block 308). In one embodiment, a wiper blade engages the printhead face 408 above the inkjet nozzle plate 410, and wipes downwardly in the same direction 208 depicted in
The silicone oil helps provide “anti-wetting” properties to the printhead face so that it resists the adhesion of liquid ink to the face plate. Additionally, the silicone oil helps reduce or prevent wear of the coating on the face plate which extends the operational lifetime of the printhead.
After completion of the wiping process, the printhead face 408 and drip bib 412 are substantially clear of ink. Process 300 next operates one or more applicators to apply low surface energy material to either or both of the printhead face 408 and drip bib 412 (block 312). As depicted in
In one embodiment, the application of low surface energy material in process 300 does not occur during every printhead maintenance cycle. For example, in an exemplary embodiment, a single application of silicone oil to the printhead face 408 has been effective for a time span of several weeks during operation of the printer. Over time the silicone oil or other low surface energy material may be worn away. The silicone oil or other low surface energy material can be applied again during a subsequent printhead maintenance operation without the need to remove the printhead from the printer. While existing printheads and drip bibs are manufactured with a low surface energy coating that can erode during operation, the low surface energy materials and methods described herein enable the printhead and drip bib to maintain a surface layer with a low surface energy during prolonged operation of the printer. The silicone oil or other low surface energy material enables the printhead and drip bib to remain substantially free of ink during operation to reduce or eliminate inkjet drooling and unwanted transfer of ink in the printer. In embodiments where the printhead has Teflon coatings disposed thereon, the silicone oil or other low surface energy material helps restore surface energy and prevents surface wetting, thus helps prevent wear of the Teflon coating. Additionally, when the silicone oil layer is applied in situ within the printer it can eliminate the need to form Teflon coatings on the printhead and drip bib during the manufacturing process.
The examples set forth hereinbelow are being submitted to illustrate embodiments of the present disclosure. These examples are intended to be illustrative only and are not intended to limit the scope of the present disclosure. Also, parts and percentages are by weight unless otherwise indicated. Comparative examples and data are also provided.
Experiments were conducted to evaluate pressure to drool over time in print heads that had Xerox Part# 093K24300 Spreader Release Fluid applied, an amino modified silicone oil, as compared to those with no silicone oil applied. The results are presented in
As can be seen in
It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
This application claims priority to U.S. Provisional Application Ser. No. 61/640,431, filed Apr. 30, 2012, which is expressly incorporated by reference. Reference is also made to commonly owned and co-pending, U.S. patent application Ser. No. ______ (not yet assigned) entitled “Methods for In Situ Applications of Low Surface Energy Materials to Printer Components” to Varun Sambhy et al., electronically filed on the same day herewith (Attorney Docket No. 20120534-417854); and U.S. patent application Ser. No. ______ (not yet assigned) entitled “Methods for In Situ Applications of Low Surface Energy Materials to Printer Components” to Michael L. Gumina, electronically filed on the same day herewith (Attorney Docket No. 20120267-417933), which are expressly incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61640431 | Apr 2012 | US |
