Printhead maintenance system

A system for receiving and recycling ink comprises a print cartridge having a printhead, and an ink supply reservoir fluidly connected to the print cartridge and a seal member coupled to the ink supply reservoir. The seal member defines a fluid path into the reservoir and the print cartridge engages the seal member so that ink spit from the printhead flows through the fluid path into the reservoir.

BACKGROUND OF THE INVENTION

Inkjet printheads require regular servicing in order to maintain the printheads and the quality of print jobs. Although there are many types of servicing systems and service stations, three pen service procedures involve wiping, spitting and capping. Wiping is a process by which the printhead nozzles are engaged with a scraper, typically rubber, to clean accumulated ink and debris off the nozzles. Spitting is a step that involves positioning the printheads over a waste ink receptacle—a spittoon—and causing the inkjet printhead to eject a volume of ink through the nozzles into the spittoon. Spittoons are simply receptacles that collect the waste ink. Sometimes spittoons are lined with absorbent material to retain the waste ink. Capping involves positioning the printheads in physical contact with a closely fitting cap—typically rubber or some other elastomer—to maintain a controlled atmosphere environment around the printheads during periods of inactivity.

Many inkjet printer service stations are configured for performing each of these three servicing tasks, and there are many variations in the order and frequency of the three servicing tasks. However, printhead servicing does not address issues relating to ink supply for the pen.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Many hardcopy devices that rely upon inkjet printing technology include service stations for maintaining the quality of the printheads, and thus the quality of the print jobs. A schematic representation of an inkjet printer according to an illustrated embodiment of the present invention is shown in the drawings. It will be appreciated that like reference numerals are used throughout the specification to identify like structural features found in more than one drawing figure.

With reference toFIGS. 1 and 2, the inkjet printer10depicts in a highly schematic manner an inkjet hard copy apparatus, in this case, a color printer. It will be appreciated that printer10includes numerous electrical and mechanical operating mechanisms that are necessary to operation of the printer, but not needed to illustrate the components or invention described herein. As such, many electrical and mechanical operating mechanisms are omitted from the drawings for clarity. An internal electronic controller90, which is usually a microprocessor or application specific integrated circuit (“ASIC”) controlled printed circuit board, administrates operation of inkjet printer10, which is connected by appropriate cabling to an external computer (not shown). It is well known to program and execute imaging, printing, print media handling, control functions, and logic with firmware or software instructions for conventional or general purpose microprocessors or ASICs. Print media12(referred to generically herein simply as “paper,” regardless of actual medium selected by the end-user, for example, cut sheet or roll stock material such as paper, film, and the like) is loaded by the end-user onto an input tray (not shown). Sheets of paper are then sequentially fed by a suitable, internal, paper-path transport mechanism to a printing station that defines a printzone14where graphical images or alphanumeric text are created using color imaging and text rendering techniques. InFIG. 1, printzone14is defined generally as the area beneath the region traversed by the inkjet print cartridges20,22,24and26where ink is applied to the paper12.

A carriage16mounted on a shaft18that has its opposite ends mounted to a printer chassis19to support in an operative position relative to paper12a set of four inkjet writing instruments, known as print cartridges, and labeled20,22,24, and26, respectively. Fewer print cartridges or more print cartridges may be used in different printers. As detailed below, each of the inkjet print cartridges20through26has at least one printhead28on the lower side of the print cartridges facing the printzone14. Each printhead28is adapted for expelling minute droplets of ink or other fluids to form dots on adjacently positioned paper12in the print zone14. Each printhead28generally consists of a drop generator mechanism and a number of columns of ink drop firing nozzles. Each column of nozzles, or a selected subset of nozzles, selectively fires ink droplets, each droplet typically being only a tiny liquid volume, that are used to create a predetermined print matrix of dots on the adjacently positioned paper as the printhead is scanned across the media. A given nozzle of the printhead is used to address a given matrix column print position on the paper. Horizontal positions, matrix pixel rows, on the paper are addressed by repeatedly firing a given nozzle at matrix row print positions as the pen is scanned across the paper. Thus, a single sweep scan of the printhead across the paper can print a swath of dots. The paper is advanced incrementally relative to the inkjet printheads to permit a series of contiguous swaths.

Inkjet printer10is shown as a full color inkjet system and therefore includes inks for the subtractive primary colors, cyan, yellow, magenta (CYM) and a true black (K). By way of example, print cartridge20contains cyan ink, print cartridge22yellow ink, print cartridge24magenta ink, and print cartridge26black ink. Different or additional colorants, such as, for example, lighter or darker shades of magenta and/or cyan, may of course be used. While the illustrated color print cartridges20,22, and24each use a dye-based ink, other types of inks may also be used, such as paraffin-based inks, as well as hybrid or composite inks having both dye and pigment characteristics.

Carriage16and thus print cartridges20,22,24and26are mounted on shaft18for shuttle-type reciprocating movement over media12. Shaft18and carriage16are mounted on printer chassis19. A carriage motor21, typically a servo motor that is connected via circuitry25to controller90and to carriage16with a drive belt27(illustrated schematically), moves or “scans” carriage16during printing in a back and forth direction transverse to the direction of media advancement through the printzone14. It is common in the art to refer to the scanning direction as the x-axis, the paper feed direction through the printzone as the y-axis, and the ink drop firing direction as the z-axis. That convention is used herein.

As noted, carriage16is under the control of the printer controller90. The position of carriage16relative to paper12in the direction along the x-axis is determined by way of an encoder strip23that has its opposite ends mounted to the printer chassis19. The encoder strip23extends past and in close proximity to an encoder or optical sensor (not shown) carried on carriage16to thereby signal to the printer controller90the position of the carriage assembly16relative to the encoder strip23.

The paper12is incrementally advanced through the printzone14by a paper transport mechanism (not shown), typically in-between scans of the carriage16. An encoder, typically a disk encoder, and associated servo systems are one of the methods often employed for controlling the precise incremental advance of the media. This incremental advance is commonly called “linefeed.” Precise control of the amount of the advance, the linefeed distance, contributes to high print quality. The paper advance mechanisms must move the paper12through the printzone14the desired distance with each incremental advance, at the desired rate, and so that the paper is oriented correctly relative to the printheads28.

Each illustrated print cartridge20,22,24and26is individually coupled to a respective ink supply main reservoir30,32,34and36, by separate flexible ink delivery tube or other conduit40,42,44and46, respectively, in what is known as an “off axis” ink delivery system. An off axis system may be contrasted with a replaceable, self-contained ink delivery system where each print cartridge has a reservoir that carries the entire ink supply as it reciprocates along the x-axis, and is thus called an “on axis” delivery system. Each pen20through26includes an on-board reservoir or chamber for holding a volume of ink that is typically smaller than the volume of ink contained in the main reservoirs30through36. The main reservoirs30through36are typically replaceable ink-in-foam or spring-in-bag designs, but other reservoir designs may also be used.

A service station shown generally and schematically in dashed lines at50services the printheads28associated with each of the pens20,22,24and26. Service station50includes a pen wiper station52and printhead seal members60,62,64and66. As detailed below, printhead seal members60through66are components of the ink supply main reservoirs30through36. Wiper station52is positioned relative to pens20through26such that when the printer controller90causes carriage16to move along the x-axis in the direction of arrow A inFIG. 1, the printheads are dragged across wiper blades58(three of which are illustrated) to effect cleaning of the printheads28. The wiper blades58physically scrape ink and contaminants off the printheads28. Wiper station52may be either stationary, or may be configured to move into an out of an operative position, typically by movement with an actuating mechanism in the direction along either the z or y-axes.

The ink supply main reservoirs30,32,34and36may be used as components of the service station50. That is, the main supply reservoirs30through36may be used to receive ink directly from the printheads28of the print cartridges20through24, recycle ink spit during servicing, and cap the printheads28during storage, in addition to supplying ink to the printheads28. It will be appreciated that because the main ink supply reservoirs30through36are located in the illustrated embodiment below the pens20through26, it may be necessary in some circumstances to include an optional pump and appropriate valves and/or sensors, illustrated generally with reference number41, to assist with delivery of ink through conduits40through46from ink supply main reservoirs30through36to the associated pens20through26. Conduits40through46are typically flexible tubing.

As may be seen inFIG. 2, and as will be detailed below, when pens20through26are being serviced and/or stored, the pens are brought into contact with a printhead seal members60through66, respectively. An actuating system33, which is shown schematically but understood to include driving means such as a motor and appropriate linkages, is provided to move ink supply main reservoirs30through36into and out of coupling engagement with printheads28, in the directions indicated with arrows B in the figures.

With reference now toFIG. 3, each ink supply main reservoir30through36includes a printhead seal member60,62,64and66, respectively, on the upper surface of the reservoir (“upper surface” referring to the surface of the reservoir facing print cartridges20through26). Thus, printhead seal member60is associated with main reservoir30; printhead seal member62is associated with main reservoir62, and so on. The printhead seal members60through66are elastomeric capping members—typically fabricated of nitrile rubbers, elastomeric silicones, ethylene polypropylene diene monomer (EPDM) and equivalent compounds—that are configured to engage a respective one of the printheads28on the print cartridges20through26to provide a fluid seal with the printheads, and to provide a desirably humid storage environment for maintaining printhead integrity, and as detailed below, for facilitating recycling of ink spit from the printheads28.

A single print cartridge, ink supply reservoir and printhead seal are illustrated inFIG. 4, in this case, pen20and the components associated therewith. Print cartridge20is schematically illustrated as defining a hollow ink-holding reservoir, internal chamber69, for holding a supply of ink71that may be expelled through printhead28. Printhead28is illustrated schematically for the sake of simplicity, and is understood to be under the control of controller90. Printhead28generally includes a plurality of drop generators73, typically thin film resistors that cause ink to be expelled in a controlled manner through corresponding ink drop firing nozzles72. The outer wall of print cartridge20defines an outer peripheral wall74that borders and surrounds printhead28. The outer surfaces of peripheral wall74are configured to form a seal with complementary wall surfaces of printhead seal member60. One such arrangement is shown inFIG. 4where the outer mating surfaces of peripheral wall74slope or taper inwardly, and the corresponding mating walls76of the printhead seal member60slope or taper correspondingly and in a complementary manner so that the respective walls74,76mate to one another and form a seal therebetween.

Referring specifically toFIG. 4, printhead seal member60is located atop ink supply reservoir30and defines a capping member having interior wall surfaces that are cooperatively configured and shaped to engage the corresponding outer peripheral wall74of print cartridge20. Thus, the inward-facing surfaces of member60define a first downwardly sloping wall section76that tapers inwardly and which is configured at an angle that is complimentary to the taper of outer peripheral wall74of print cartridge20such that when the supply reservoir30is moved into the position where seal member60engages print cartridge20, as shown inFIG. 4, a fluid-tight seal is formed between the print cartridge20and the printhead seal member60. Printhead seal member60includes a second downwardly sloping wall section78interiorly of wall section76. Thus, with reference to the direction inFIG. 4moving from first downwardly sloping wall section76toward the center portion of the seal member60, the second downwardly sloping wall section78terminates at an opening80that communicates through the seal member60into supply reservoir30to define a fluid path77from print cartridge20to ink70held in reservoir30. A filter82is positioned within reservoir30in the fluid path. The printer controller90and actuator33cooperate to move reservoir30in the direction indicated by arrows B in order to move the reservoir30into a sealing relationship between the printhead seal member60and the printhead28as shown.

When the printer controller90determines that a printhead28needs to spit to maintain the health of nozzles72, or for some other reason servicing is required, the controller90causes carriage16to be positioned relative to the ink supply reservoirs30through36such that the printheads28are aligned over the corresponding printhead seal members60,62,64and66. When the print cartridges20through26and their associated printheads28and the associated printhead seal members60through66are aligned, controller90causes carriage motion to stop, and the controller90and actuator33cooperate to move reservoirs30through36upwardly as indicated with arrow B inFIG. 4until each of the printhead seal members60through66are in the position shown inFIG. 4. In this position a fluid-tight seal is formed between each of the print cartridges20through26and the associated printhead seal members60through66. It should be noted that while in most instances the physical engagement between the printhead seal members60through66and the corresponding printheads28provides a fluid tight sealed engagement therebetween, spitting may be accomplished with the printheads28and printhead seal members60through66in close proximity to one another rather than in a sealed relationship. The controller90then causes ink to be spit by the selected printhead nozzles72into printhead seal member60.

Ink71spit from printhead28is illustrated schematically inFIG. 4with dotted lines84. The first and second downwardly sloping walls76and78of the printhead seal member60cause the ink71to flow into opening80, through fluid path77, through a filter82and into the supply of ink70contained in main reservoir30. Any contaminants carried by the ink70or introduced from other sources are captured by the filter82and are therefore prevented from entering the supply of ink70or delivery conduit40. Spit ink71from pen20is thus mixed with ink70residing in the supply reservoir30and is recycled since it is again available to be drawn into delivery conduit40and reintroduced into chamber69of print cartridges20. The controller90is configured for initiating spitting for any of the printheads on an individual basis, or for all of the printheads together. During the periods of time when the pens are separated from the printhead seal members, as for example during active printing operations, filter82serves as a plug or seal that retards any evaporation of ink70from the supply reservoir30.

By recycling the ink in the manner just described, overall consumer ink costs are reduced and the printer need not be taken out of service to eliminate waste ink in a spittoon. Moreover, the mess associated with waste ink in spittoons, and possible environmental consequences of throwing out waste ink, are eliminated. And by eliminating the hardware associated with spittoons and the associated mechanisms, valuable space in the printer housing are freed up for other components, or for reduction in the size and cost of the printer. Finally, since the print cartridges20through26are brought into a sealing engagement with the printhead seal members60through66when spitting occurs, any ink aerosolized during spitting is recycled, eliminating the risk that ink thus expelled from one printhead28may cross contaminate adjacent printheads28.

After spitting as described above, the print cartridges20may return to printing, undergo other servicing, or be capped for storage. It will be appreciated that in the case where the print cartridges20through26are to be stored after spitting, then the sealing engagement described above between print cartridges20through26and printhead seal members60through66is maintained. When the print cartridges20through26and their associated printheads28are to be stored between periods of printing, the carriage16and print cartridges20through26are positioned over the ink supply reservoirs30through36as shown inFIG. 1. Controller90in cooperation with actuator33moves supply reservoirs30through36upwardly (in the direction of the z-axis indicated with arrows B) so that the printhead seal members60through66are brought into contact with the print cartridges20through26as previously described. The sealing engagement between the print cartridges20through26and the associated printhead seal members60,62,64and66creates a controlled environment around the printhead nozzles that helps maintain printhead health. Specifically, when the print cartridges20through26are in a sealing engagement with the seal members60through66, which communicate via openings80and fluid paths77with a large reservoir of ink70contained in the main reservoirs30through36, as shown and described, the ambient pressure and humidity conditions surrounding the printhead28during storage are favorable and promote long printhead life. Thus, the humidity is controlled around the printheads28not only by the ink present in the nozzles72, but also by the fluid communication with the relatively large reservoir of supply ink70. The desirable humid environment thus created and maintained helps to reduce ink thickening at the nozzles. Finally, during storage, ink is often and inevitably drooled from a printhead28. When the printheads28are capped as described above with printhead seal members60through66, drooled ink flows back into the ink supply reservoirs through openings80where it is recycled in the same manner as ink that is intentionally spit from the nozzles72.

In the embodiment illustrated inFIGS. 1 through 4, each ink supply reservoir30through36includes a separate printhead seal member,60through66, which seals over a separate printhead28on an associated pen20through26. It will be appreciated that the printhead seal members may be fabricated in a single piece. An alternate embodiment of the invention showing a single piece printhead seal member is illustrated inFIGS. 5 and 6. With reference to those drawings, the individual printhead seal members60through66have been replaced with a single printhead seal member100that is fabricated to fit atop each of the four ink supply main reservoirs30through36. Apart from being fabricated in a single piece that engages all of the ink supply main reservoirs, printhead seal member100is substantially the same as the individual printhead seal members30through36as detailed above. As shown in the partial fragmentary view ofFIG. 6, printhead seal member100defines four capping members, one for each of the printheads28associated with pens20through26. Because the seal member100is fabricated in a single piece, a partition102is provided between adjacent pens, such as the partition102between pens20and22shown inFIG. 6. Partition102is fabricated as an integral part of seal member100.

It will be appreciated that single-piece printhead seal member100may be used in a printer that utilizes more or less pens than the four illustrated herein.

The ink supply reservoirs30through36are replaceable. The printhead seal members may be fabricated such that they are replaced when the ink supply reservoirs are replaced, or the seal members may be reused on the replacement reservoirs if desired. The printhead seal members may thus be made as replaceable consumable components, as reusable components, or as permanent components or any combination.

Although preferred and alternative embodiments of the present invention have been described, it will be appreciated by one of ordinary skill in this art that the spirit and scope of the invention is not limited to those embodiments, but extend to the various modifications and equivalents as defined in the appended claims.