The system described below relates to imaging devices that produce ink images on a continuous web of media, and, more particularly, to cleaning accumulated ink off surfaces within the imaging devices.
In general, inkjet printing machines, also known as imaging devices or printers, include at least one printhead that ejects drops of liquid ink either directly onto recording media or onto an ink image receiving surface for transfer to recording media. A phase change inkjet printer employs phase change inks that are in the solid phase at ambient temperature, but they transition to a liquid at an elevated temperature. The melted ink is then ejected as ink drops by a printhead to form an ink image.
One type of inkjet printer is a continuous web printer. In this type of printer, a media web is unwound from a supply roller and directed through a feed path that passes by one or more printheads for formation of an ink image directly onto the sheet. The continuous web is pulled through the printer by driven rollers. Tension is maintained on the web to enable movement of the web by moveable tension bars or rollers, which remove slack from the web so the web remains taut without breaking.
Regardless of the type of media, proper image durability and quality is achieved by heating the media both prior to printing and fixing the ink image onto the web. In web-fed printers, media heaters typically comprise one or more radiant heaters positioned along the media pathway for exposing the media to a sufficient amount of thermal energy to regulate the temperature of the moving web. Thermal output of the radiant heaters is controlled by adjusting the power supplied to the heaters. The printing system typically includes a thermal sensor positioned adjacent the media pathway to detect the temperature of the moving web and provide the detected temperatures to a controller. The controller can then adjust the electrical power provided to the heaters with reference to the detected temperatures of the web to adjust the temperature of the media web.
A schematic diagram for a typical continuous web printer that includes multiple printheads that eject melted phase change ink on the moving web to form an ink image on the web is illustrated in
The web supply and handling system 160 can include one or more media supply rolls 138 for supplying a media web 112 to the printer 110. The supply and handling system 160 is configured to feed the media web 112 in a process direction 130 in a known manner along a media pathway in the printer 110 through the print zone 118, and past the web heating system 120 and fixing assembly 150. To this end, the supply and handling system 160 can include any suitable arrangement of components 164, such as rollers, idler rollers, tensioning bars, etc., for moving the media web 112 through the printer 110. The web supply and handling system 160 can include a take-up roller 139 for receiving the media web 112 after printing operations have been performed.
The phase change ink printing system 114 includes a plurality of printhead assemblies, which are appropriately supported to enable one or more printheads within these assemblies to eject drops of ink directly onto the media web 112 as the web moves through the print zone 118. The printing system 114 can be incorporated into either a carriage type printer, a partial width array type printer, or a page-width type printer.
Ink is supplied to the printhead assemblies within the printing system 114 from a solid ink supply (not shown). Since the phase change ink printer 110 is a multicolor device, the ink supply includes multiple sources of different colors of phase change solid ink. The phase change ink system also includes a solid phase change ink melting assembly (not shown) for at least each color of ink to melt and deliver liquid ink to one of the printhead assemblies in the printing system 114. The liquid ink is supplied to one or more printheads in a printhead assembly by gravity, pump action, or both.
Once the drops of ink have been ejected by the printing system 114 onto the moving media web 112 to form an ink image, the media web 112 is moved through a fixing assembly 150 which spreads the ink enabling proper image durability and quality. In the embodiment of
Operation and control of the various subsystems, components, and functions of the printer 110 are performed with the aid of a controller (not shown in
In the embodiment of
The web heating system 120 can be configured to heat the media web 112 to any suitable temperature dependent upon a number of factors including web speed, web type, ink type, position along the media pathway, etc. For example, the web heating system 120 can be configured to heat the media web 112 to approximately 55 degrees Celsius at the preheating drum 124 prior to printing to the web. The web heating system 120 can also be configured to heat the media web 112 to approximately 30 degrees Celsius at the leveler roller 126.
Ink sometimes escapes from the printhead assemblies in the printing system 114 and migrates to the surface of the preheating drum 124 or the leveler roller 126. Even the intermittent release of melted ink onto one or both of these rollers can accumulate to a level capable of producing defects on prints by interfering with the movement of the media web 112 about the preheating drum 124 and/or the leveler roller 126. Manually cleaning accumulated ink from the preheating drum 124 or leveler roller 126 is a time consuming and labor intensive process because features within the printer 110 are difficult to access without dismantling at least part of the printer 110. Additionally, the printer 110 cannot be used to generate printed images when the drum 124 or the leveler 126 is manually cleaned. Accordingly, a process for cleaning ink off the preheating drum 124 and/or the leveler roller 126 that minimally interferes with use of the printer is desirable.
A method of cleaning a heated drum within a continuous web printer has been developed. The method includes operating an actuator to rotate a drum heated to a first temperature, stopping movement of the media web, heating the drum to a second temperature that is greater than the first temperature, and operating the actuator to rotate the drum against a portion of the stopped media web to transfer ink from the drum to the portion of the stopped media web. The drum rotates in a process direction of a media web and the drum contacts the media web to heat the media web as the media web moves over a portion of the drum.
A continuous web printer configured to clean a heated drum within the continuous web printer has been developed. The continuous web printer includes a first actuator, a drum, a heater, a second actuator, and a controller. The first actuator is operatively connected to and configured to rotate the drum. The heater is configured to heat the drum. The second actuator is operatively connected to a roller to move a continuous media web through the continuous web printer. The controller is operatively connected to the first actuator, the heater, and the second actuator. The controller is configured to operate the heater to heat the drum to a first temperature, to operate the first actuator and the second actuator to rotate the drum while the drum is heated to the first temperature and move the continuous media web through the continuous web printer to enable ink image formation on the continuous media web, to stop the second actuator and movement of the continuous media web through the continuous web printer, to operate the heater to heat the drum to a second temperature that is greater than the first temperature, and to operate the first actuator to rotate the drum against a portion of the stopped continuous media web to transfer ink from the drum to the portion of the stopped continuous media web.
a depicts the leveler roller and media web of
b depicts the leveler roller and media web of
c depicts the leveler roller and media web of
The leveler roller 226 engages the media web 212 after an ink image has been formed on the media web 212 and heats the media web 212 to bring the different layers of ink on the media web 212 to a uniform temperature. The leveler roller actuator 272 is operatively connected to the leveler roller 226 to rotate the leveler roller 226 in a clockwise direction 232 to move the media web 212 around the leveler roller 226 and through the portion 210 in the process direction 230. The tension roller 264 engages the media web 212 downstream from the leveler roller 226 to maintain the appropriate amount of tension in the media web 212 through the portion 210. In the embodiment shown in
The optical sensor 240 is positioned downstream from the leveler roller 226 and generates image data of the surface of the media web 212 facing the sensor. The optical sensor 240 can be, for example, an image on web array (IOWA) sensor which includes a plurality of photoreceptors arranged in a linear array in a direction perpendicular to the process direction 230. When ink is on the media web 212, light is absorbed or scattered away from the sensor and when ink is not on the media web 212, light is reflected into the photoreceptor opposite the bare web reflecting the light. Each photoreceptor in the optical sensor 240 generates a signal having an amplitude that corresponds to the amount of reflected light received by the photoreceptor. Thus, the signals generated by the optical sensor 240 correspond to the presence or absence of ink opposite the optical sensor. The controller 270 receives these signals as image data. The controller 270 can execute programmed instructions stored in a memory operatively connected to the controller to analyze these image data.
The media web roller 266 is positioned downstream from the leveler roller 226 and engages the media web 212 to move the media web 212 through the portion 210. In the embodiment shown in
The preheating drum 324 heats the media web 212 to a predetermined temperature before an ink image is formed on the media web 212. The preheating drum actuator 373 is operatively connected to the preheating drum 324 to rotate the drum 324 in a clockwise direction 332 to move the media web 212 around the preheating drum 324 and through the portion 310 in the process direction 330. The tension roller 364 engages the media web 212 upstream from the preheating drum 324 to maintain the appropriate amount of tension in the media web 212 through the portion 310. In the embodiment shown in
The media web roller 366 is positioned upstream from the preheating drum 324 and engages the media web 212 to move the media web 212 through the portion 310. In the embodiment shown in
As described above, ink can be unintentionally transferred to and accumulate on the surface of the preheating drum 324 (shown in
First, transferred ink on the leveler roller 226 is detected in one of two ways with the controller 270 (block 404). The first way that transferred ink can be detected is by a user who finds unintended ink on prints. The user then inputs information corresponding to the unintended ink into the user interface 278. The user interface 278 generates a signal indicating ink on the leveler roller 226 and sends the signal to the controller 270. The controller 270 receives the signal from the user interface 278 and acknowledges the transferred ink. The second way that transferred ink can be detected is by the optical sensor 240. Data corresponding to the intended image to be printed can be received by the controller 270. The optical sensor 240 can then generate signals that are provided to the controller 270 as image data corresponding to the actual image that was printed. These image data are analyzed by the controller 270 to detect the presence of ink in a print that was not ejected by the printing system 114 on the web 212.
In one embodiment, the controller 270 initiates a cleaning process in response to the detection of ink not ejected onto the web 212. In an alternative embodiment, the controller 270 can initiate the cleaning process periodically, regardless of the presence of transferred ink. Regardless of the method used to initiate the cleaning process, the process begins with the controller 270 operating the actuators operatively connected to the controller to stop the media web 212 from moving through the printer (block 408). The controller 270 then operates the tension roller actuator 274 to apply a predetermined pressure to the stopped media web 212 with the tension roller 264, making the media web 212 taut through the portion 210 without breaking (block 412). The controller 270 then adjusts the electrical power to the heater 278 to increase the temperature of the leveler roller 226 to a predetermined temperature that renders the ink on the leveler roller more malleable (block 416). For example, in one embodiment, the temperature of the leveler roller is raised to 80 degrees Celsius. The increased temperature of the leveler roller 226 softens the solidified accumulated ink, which causes the ink to undergo a phase transition to a semi-fluid state. The controller 270 then operates the leveler roller actuator 272 to rotate the leveler roller 226 relative to the taut, stationary media web 212 (block 420). Rotating the leveler roller 226 relative to the media web 212 causes the media web 212 to rub the surface of the leveler roller 226. The tautness of the media web 212 over the leveler roller 226 produces friction between the surface of the leveler roller 226 and the web 212 so the semi-fluid accumulated ink is rubbed off the surface of the leveler roller 226 and onto the media web 212. After all or most of the ink is transferred to the stationary web portion rubbing against the leveler roller, the controller operates the actuators operatively connected to the controller to resume movement of the web through the printer so the portion now bearing the accumulated ink is carried out of the printer (block 424).
In a similar manner, the printer portion 310 can be operated to clean accumulated ink from the pre-heating drum 324. Again with reference to
While a printer can be configured with only one of the processes described above to clean either the leveler roller only or the pre-heating roller only, other embodiments configure two controllers or a single controller for independent implementation of the processes. In these embodiments, the controller(s) are capable of cleaning both the pre-heating roller and the leveler roller independently of one another. In yet another embodiment, the controller(s) are configured to perform the two processes simultaneously. Such an embodiment reduces the time for cleaning both the pre-heating drum and the leveler roller.
a-4c depict a chronological view of the media web 212 and the leveler roller 226 during the cleaning process.
Referring again to
Those skilled in the art will recognize that numerous modifications can be made to the specific implementations described above. Therefore, the following claims are not to be limited to the specific embodiments illustrated and described above. The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
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