This disclosure relates generally to inkjet printers that eject ink to form ink images on print media, and, more particularly, to devices that clean ink from printheads in such printers.
In general, inkjet printers include at least one printhead that ejects drops of liquid ink onto recording media or a surface of an image receiving member. In an indirect or offset printer, the inkjets eject ink onto the surface of the image receiving member, such as a rotating metal drum or endless belt, and then the image is transferred to print media. In a direct printer, the inkjets eject ink directly onto the media, which may be in sheet or continuous web form. A phase change inkjet printer employs phase change inks that are solid at ambient temperature, but transition to a liquid phase at an elevated temperature. Once the melted ink is ejected onto the media or image receiving member, depending upon the type of printer, the ink droplets quickly solidify to form an ink image.
Printers typically conduct various maintenance operations to ensure proper operation of the inkjets in each printhead. One known maintenance operation removes particles or other contaminants that may interfere with printing operations from each printhead in a printer. During such a cleaning maintenance operation, a pneumatic fluid, such as air, is forced into the printheads to purge ink through some or all of the inkjets in the printhead. The purged ink flows from the apertures of the inkjets that are located in a faceplate of each printhead onto the faceplate of each printhead. The ink flows downwardly under the effect of gravity to an ink drip bib mounted at the lower edge of the faceplate. The bib is configured with one or more multiple drip points where the liquid ink collects and drips into an ink receptacle. One or more wipers are manipulated to contact the faceplate of each printhead and wipe the purged ink toward the drip bib to facilitate the collection and removal of the purged ink.
Some printers have been equipped with a flexure chute that is moved into contact with the faceplate below the apertures during a cleaning operation. The chute is used to deflect purged and/or wiped ink away from the faceplate and into a catch tray. While this system sufficiently removes ink from the aperture area of the faceplate, a line of ink (i.e., witness line) may remain on the faceplate surface of the printhead where the flexure chute contacts the faceplate. This witness line of residual ink accumulates further with time and repeated maintenance cycles. Eventually, the accumulated ink can run down the drip bib surface and coalesce at the drip points or be forced onto the aperture area of the faceplate by airflow caused by print media moving past the printhead. Accumulated ink at the drip points may eventually freeze and fall into the paper path where it can impact print quality and potentially cause damage to printheads. Thus, improved systems and methods for preventing the accumulation of purged ink on the faceplates of printheads are desirable.
To address difficulties associated with residual ink contamination on the printhead faceplate and drip bib, a printhead cleaning device is provided that includes a flexure chute having a first end and a second end, and an ink receptacle in which the second end of the flexure chute is positioned to enable ink to flow from the first end of the flexure chute along one side of the flexure chute into the ink receptacle. The cleaning device includes a length of absorbent material positioned near the first end of the flexure chute with the length of the absorbent material being approximately a same distance as a width across the printhead array.
In another embodiment, a method of operating a cleaning device of an inkjet printer includes pressing a first end of a flexure chute of a cleaning device against a faceplate of a printhead at a first position, the flexure chute including a second end positioned over an ink receptacle. A length of absorbent material of the cleaning device is then pressed against the faceplate at a second position which is below the first end of the flexure chute with the length of absorbent material being approximately a same distance as a width across the printhead array.
For a general understanding of the present embodiments, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to designate like elements. As used herein, the terms “printer” generally refer to an apparatus that applies an ink image to print media and may encompass any apparatus, such as a digital copier, bookmaking machine, facsimile machine, multi-function machine, etc. which performs a printing function for any purpose.
As used in this document, “ink” refers to a colorant that is liquid when applied to an image receiving member. For example, ink may be aqueous ink, ink emulsions, solvent based inks and melted phase change inks. Phase changes inks are inks that are in a solid or gelatinous state at room temperature and change to a liquid state when heated to a melting temperature. The melted ink can then be applied or ejected onto an image receiving member. The phase change inks return to a solid or gelatinous state when cooled on print media after the printing process. “Print media” can be a physical sheet of paper, plastic, or other suitable physical substrate suitable for receiving ink images, whether precut or web fed.
As used herein, the term “direct printer” refers to a printer that ejects ink drops directly onto a print medium to form the ink images. As used herein, the term “indirect printer” refers to a printer having an intermediate image receiving member, such as a rotating drum or endless belt, which receives ink drops that form an ink image. In the indirect printer, the ink image is transferred from the indirect member to a print medium via a “transfix” operation that is well known in the art. A printer may include a variety of other components, such as finishers, paper feeders, and the like, and may be embodied as a copier, printer, or a multifunction machine. Image data corresponding to an ink image generally may include information in electronic form, which is to be rendered on print media by a marking engine and may include text, graphics, pictures, and the like.
The term “printhead” as used herein refers to a component in the printer that is configured to eject ink drops onto the image receiving member. A typical printhead includes a plurality of inkjets that are configured to eject ink drops of one or more ink colors onto the image receiving member. The inkjets are arranged in an array of one or more rows and columns. In some embodiments, the inkjets are arranged in staggered diagonal rows across a face of the printhead. Various printer embodiments include one or more printheads that form ink images on the image receiving member. As used herein, the term “process direction” refers to the direction in which the substrate onto which the image is transferred moves past the printheads for formation of an ink image. The term “cross-process direction” refers to a direction, along the same plane as the substrate, which is substantially perpendicular to the process direction.
Cleaning unit 200 includes a housing, shown here as support rails 244 and 246 and ink receptacle 240, a flexure chute assembly 254, a cleaning web system 300, and printhead wiper units 204, 220, 224, and 228. Support rails 244 and 246 maintain ink receptacle 240 in place and support the wiper units 204, 220, 224, and 228. Ink receptacle 240 is a container that forms a volume with a sufficient size to hold ink purged from each of the printheads 104, 120, 124, and 128 in printhead array 100 during cleaning operations. The top 242 of the ink receptacle 240 is open to enable ink purged from printheads in the printhead array 100 to flow into the ink receptacle 240. While cleaning unit 200 includes a single ink receptacle 240, alternative cleaning unit embodiments can employ two or more receptacles. Rails 244 and 246 include docking members 270 and 280, respectively. The docking members 270 and 280 are configured to engage docking balls 132 and 140, respectively, on the printhead array 100 to secure the printhead array 100 to the cleaning unit 200 during purge and cleaning operations.
In the embodiment of
The ink receptacle 240 is configured to receive ink from printhead array 100 through the open top 242. The flexure chute assembly 254 includes a flexure chute 256 for each printhead unit 104, 120, 124, 128 in the printhead array 100. The flexure chute assembly 254 extends through the housing opening 242 to enable each flexure chute 256 to contact the face 108 of the corresponding printhead unit. Each flexure chute 256 has a width that is sufficient to extend across the face of the printhead unit as the printhead array 100 engages and disengages with the cleaning unit 200. The flexure chutes 256 of the illustrated embodiment comprise rectangular plates, although any shape and size capable of capturing ink purged from the printheads may be used. The flexure chutes 256 can be formed of stainless steel or any other material suitable to direct ink from a printhead to an ink receptacle.
In the configuration of
The flexure chute 256 has a first end 257 and a second end 258. The first end 257 is located at a position inside the ink receptacle 240 that enables gravity to pull ink from the second end 258 of the flexure chute 256 into the ink receptacle 240. The second end 258 of the flexure chute 256 is configured to engage the printhead faceplate 108 during cleaning and maintenance in order to collect ink emitted from the apertures onto the faceplate during a purge process.
During purge operations, the receptacle 240 is positioned close enough to the faceplate 108 to enable the second end 258 of the chute 256 to contact the faceplate 108 at a position below the apertures in the faceplate, but above the juncture between the drip bib 110 and the faceplate 108. Pressure applied to the reservoir within the printhead urges ink 264 through the inkjets to the apertures in the faceplate 108. This pressure does not eject the ink, but rather releases ink onto the faceplate 108. This action helps unclog the inkjets, dissolve debris or solidified ink on the faceplate, and act as a lubricant for the wiper. Once the purged ink 264 flows down the printhead face 108 to the juncture with the second end 258 of the flexure chute 256, the flexure chute 256 guides the ink 264 into the ink receptacle 240.
Wiper 204 and wiper blade 208 are also moved into contact with the faceplate 108 above the apertures for the inkjets and swiped downwardly in direction 290 to direct any ink 264 remaining on the printhead face 108 onto the flexure chute 256 and into the ink receptacle 240.
In accordance with the present disclosure, a cleaning web system 300 is incorporated into the cleaning unit 200 for removing purged ink that can accumulate on the faceplate 108 at a position where the faceplate 108 is contacted by the flexure chute 256. Referring to
The cleaning web system 300 includes a cleaning web support assembly 308 that is configured to support the cleaning web 304 with the web extended across the printhead unit (in the cross-process direction) between the lower portion of the face plate and drip bib of the printhead and the flexure chute of the cleaning station. The cleaning web 304 is supplied from a feed cartridge 310 that is supported by the support rail 246 of the cleaning unit 200. A take-up cartridge 312 is supported by the support rail 244 at the other end of the cleaning unit 200 for taking up and storing the cleaning web 304 pulled from the feed cartridge 310.
The support assembly 308 may include various structures for defining the position, orientation, and path of movement of the cleaning web 304 in relation to the faceplate 108 and the flexure chute 256. For example, in the embodiment of
In the embodiment of
In one embodiment, the witness mark cleaning system includes a pressing member 316 for pressing the cleaning web 304 against the face plate 108 and the drip bib 110 to facilitate the absorption of purged ink. The pressing member 316 can comprise a pliable structure, such as a foam spacer, that is supported on the side of the flexure chute opposite the side on which purged ink flows into the receptacle 240. The pressing member 316 is positioned to urge the cleaning web 304 against the drip bib 110 when the flexure chute 256 is at or near the faceplate 108. In some embodiments, the pressing member 316 is used alone to absorb purged ink from the faceplate without a cleaning web 304 being provided.
The feed and take-up cartridges 310, 312 of the cleaning web system 300 each include an indexing drive mechanism that enables a predetermined length of the cleaning web 304 to be unwound by the feed cartridge 310 and taken up by the take-up cartridge 312 for each docking cycle between the printhead array 100 and the cleaning unit 200. An embodiment of a cartridge having an indexing drive system for implementing the feed and take-up cartridges 310, 312 is depicted in
The cartridge 310, 312 includes a housing (not shown) for supporting a mandrel 324, a ratchet wheel 326, a ratchet pawl 328, and a drive mechanism 330, so the components can be installed and removed from the cleaning station of the printer as a unit. The mandrel 324 comprises a rotatable member, such as a tube or shaft, upon which the cleaning web is wound or from which the cleaning web is unwound depending upon whether the cartridge is a feed or take-up cartridge. The mandrel 324 is supported in the cartridge for rotation about an axis A. A ratchet wheel 326 is fixedly attached to at least one end of the mandrel 324 for rotation with the mandrel 324 about the axis A. The ratchet pawl 328 is mounted in position to interact with the ratchet wheel 326. The ratchet wheel 326 and ratchet pawl 328 are configured to interact to enable rotation of the mandrel 324 about the axis A in a first direction and to prevent rotation of the mandrel 324 about the axis A in the opposite direction.
The indexing drive mechanism 330 is operably connected to the mandrel 324 for rotating the mandrel 324 in the first direction in predetermined angular increments. In one embodiment, the indexing drive mechanism includes a one-way clutch 332, a link arm 334, and an actuator 336. The clutch 332 is shown in phantom since it is located behind the ratchet wheel 326. One end of the link arm 334 is supported for rotation about the axis A of the mandrel 324 while the other end of the link arm 334 is attached to the actuator 336. The one-way clutch 332 connects the mandrel 324 to the link arm 334 when the link arm 334 is pivoted about the axis in the first direction and disconnects the mandrel 324 from the link arm 334 when the link arm 334 is pivoted about the axis A in the opposite direction.
When the link arm 334 is pivoted about the axis A in the first direction, the mandrel 324 is locked to the link arm 334 and is rotated about the axis A in the first direction along with the link arm. Rotational movement of the mandrel 324 in the first direction may be used to let out a length of the cleaning web 304 in the case of the feed cartridge 310 and may be used to take up a length of the cleaning web in the case of the take-up cartridge 312. An actuator 336 is configured to pivot the link arm 334 about the axis A between a first angular position and a second angular position. The distance between the first and second positions of the link arm 334 controls the length of cleaning web that is let out by the feed cartridge 310 and taken up by the take-up cartridge 312 when the link arm 334 is cycled from the first position to the second position.
Movement of the link arm 334 from the first to the second position causes the mandrel 324 to be indexed from one angular incremental position to the next angular incremental position. When the link arm 334 is pivoted from the second position to the first position, the mandrel 324 is disconnected from the link arm 334 by the one-way clutch 332 and is allowed to rotate with respect to the link arm 334. Backward rotation of the mandrel 324 is prevented by interaction between the ratchet wheel 326 and the ratchet pawl 328. As a result, the mandrel 324 is retained at the angular position reached the last time the link arm 334 was cycled from the first position to the second position.
In one embodiment, the indexing drive mechanism 330 is configured for pneumatic actuation. The cleaning unit 200 of the printer already has a pneumatic system in place for use in maintenance operations, such as wiper actuation and/or purging operations. This system can be adapted in a simple manner for use actuating the indexing drive mechanism. An embodiment of a pneumatic actuator for the indexing drive mechanism of a cartridge is depicted in
The piston 340 is configured to be moved to the retracted position in response to pressurized fluid being delivered into the cylinder 338. The piston 340 is returned to the extended position by the biasing member 342 when pressurized fluid is discharged from the cylinder 338. The outer end of the piston is attached to the link arm 334. When the piston 340 is retracted into the cylinder 338, the piston 340 pulls the link arm 334 from the first position to the second position. When the piston 340 is extended from the cylinder 338, the piston 340 pushes the link arm 334 from the second position to the first position.
In the embodiment of
The pneumatic valve 344 is operated by a switch 356, such as a microswitch, that is configured to control the position of the pneumatic valve. The switch 356 can control the valve position in any suitable manner. In one embodiment, the switch 356 is configured to move the pneumatic valve 344 to the open position in response to the printhead array 100 being docked. For example, the switch 356 may be placed in a position where it can be activated, e.g., depressed, by a portion of the housing or casing of the printhead array 100 once the printhead array 100 has been docked with the cleaning unit 200.
When the switch 356 is depressed, the pneumatic valve 344 is opened and fluid is delivered to the pneumatic cylinder 336. During operation of the web cleaning system 300, the pressurized fluid is supplied to the pneumatic cylinders of the feed cartridge 310 and the take-up cartridge 312. The supply of pressurized fluid to the cylinders 338 causes the pistons 340 in the cylinders to be moved from extended positions to retracted positions. The pistons in turn pull the respective link arms 334 from the first position to the second position.
In the feed cartridge, movement of the link arm 334 from the first position to the second position causes the associated mandrel 324 to rotate from one incremental angular position to the next incremental angular position and let out a predetermined length of the cleaning web 304. In the take-up cartridge, movement of the link arm 334 from the first position to the second position causes the associated mandrel 324 to rotate from one incremental angular position to the next incremental angular position and take up the same predetermined length of the cleaning web. When the printhead array 100 is undocked from the cleaning unit 200, the switch 356 is deactivated and the pneumatic valve 344 returns to the closed position. As a result, the fluid under pressure in the cylinder 338 escapes via the exhaust outlet 354 of the valve 344 and the link arm 334 returns to the first position.
The length of the web that is dispensed and taken up during each cycle of the link arm depends on a number of factors, such as the diameter of the mandrel and configuration of the link arm. Any suitable sizing and dimensioning of these components may be used to enable a suitable length of cleaning web to be wound and unwound during each cycle of the link arm. Although the link arm 334 is depicted as a simple lever in
In one embodiment, the drive mechanism is configured to actuate the link arm 334 to rotate the mandrel a single time when the switch 356 is activated during a docking sequence of the printhead array 100. In alternative embodiments, the drive mechanism may be configured to actuate the link arm multiple times when the switch is activated in order to wind or unwind a desired length of the web. Any suitable method or system may be used to enable the link arm to be cycled multiple times during a docking sequence. For example, pneumatic control components and valving may be used to cycle the link arm multiple times by periodically evacuating the cylinder. Although the drip management system described above can be incorporated into a printer without having to add additional electrical or control dependencies, electronic control mechanisms, such as electronic valves and/or timers, may be used to enable the link arm to be cycled as well as to synchronize the cycling of the link arms in both the feed and take-up cartridges if desired.
In addition, in some alternative embodiments, other types of switches and/or sensors may be used to actuate the indexing mechanism based on the position of the printhead array or the position and/or operational state of other components of the printer. In addition, although pneumatic actuation has been described for use in the indexing drive mechanism, other forms of actuation can be used in alternative embodiments, such as electrical and electromechanical actuation. For example, an electromechanical solenoid can be used to control the movement of the link arm in conjunction with the appropriate electric switches, controls, processors, and/or software components.
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.
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Number | Date | Country | |
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20150062241 A1 | Mar 2015 | US |