Patent Application
20250214352
This disclosure relates generally to devices that produce aqueous ink images on media, and more particularly, to the production of ink images on coated media in such devices.
Inkjet imaging devices, also known as inkjet printers, eject liquid ink from printheads to form images on an image receiving surface. The printheads include a plurality of inkjets that are arranged in an array. Each inkjet has a thermal or piezoelectric actuator that is coupled to a printhead controller. The printhead controller generates firing signals that correspond to digital data content corresponding to images. The actuators in the printheads respond to the firing signals by expanding into an ink chamber to eject ink drops onto an image receiving surface and form an ink image that corresponds to the digital image content used to generate the firing signals. The image receiving surface is usually a continuous web of media material or a series of media sheets.
Inkjet printers used for producing color images typically include multiple printhead assemblies. Each printhead assembly includes one or more printheads that usually eject a single color of ink. In a typical inkjet color printer, four printhead assemblies are positioned in a process direction with each printhead assembly ejecting a different color of ink. The four ink colors most frequently used are cyan, magenta, yellow, and black. The common nomenclature for such printers is CMYK color printers. Some CMYK printers have two printhead assemblies that print each color of ink. The printhead assemblies that print the same color of ink are offset from each other by one-half of the distance between adjacent inkjets in the cross-process direction to double the number of pixels per inch density of a line of the color of ink ejected by the printheads in the two assemblies. As used in this document, the term “process direction” means the direction of movement of the image receiving surface as it passes the printheads in the printer and the term “cross-process direction” means a direction that is perpendicular to the process direction in the plane of the image receiving surface.
Image quality in color inkjet printers depends upon on many factors such as ink chemistry, printhead technology, thermals in the vicinity of the ink drops, print process setpoints, airflows, and ink-to-media spreading and drying interactions. One issue that degrades image quality is the level of overlay graininess that results when ink images are printed on coated media or stocks. At current media speeds in the vicinity of 850 mm/second, drying aqueous ink drops on some coated media sheets requires drying at temperatures of about 100° C.±5° C. for at least two seconds and with some media sheets longer periods of time for heat exposure would be required. Currently known inkjet printer dryers are not long enough to provide high temperature exposure for this required minimum time. Adding additional dryers in series to increase the length of the dryer and the time that the media sheets are within the dryers is not feasible as these additional dryers add considerable expense to the price of the printers and substantially increase the footprint of the printer. Reducing the effect of media coating on ink image quality during aqueous ink image printing without these adverse impacts would be beneficial.
An image dryer for a color inkjet printer is configured to move media sheets bearing aqueous ink images vertically through the image dryer to expose the media sheets to temperatures of about 100° C.±5° C. for at least two seconds before returning the media sheets to a media transport that carries the sheets through the inkjet printer. The image dryer includes a housing having a first opening configured to receive media sheets from a media conveyor and a second opening that is vertically displaced from the first opening at a position that is higher than the first opening; and a media conveyor configured to move the received media sheets within the housing from the first opening to the second opening.
An inkjet printer is configured with an image dryer that moves media sheets bearing aqueous ink images vertically through a dryer that is configured to expose the media sheets to temperatures of about 100° C.±5° C. for at least two seconds before returning the media sheets to a media transport that carries the sheets through the inkjet printer. The inkjet printer includes at least one printhead; a media transport for moving a media sheet through a print zone opposite the at least one printhead in a process direction; an image dryer that follows the at least one printhead in the process direction. The image dryer having a housing having a first opening configured to receive media sheets from a media conveyor and a second opening that is vertically displaced from the first opening at a position that is higher than the first opening; and a media conveyor configured to move the received media sheets from the first opening to the second opening within the housing.
The foregoing aspects and other features of an image dryer and an inkjet printer that moves media sheets bearing aqueous ink images vertically through a dryer that is configured to expose the media sheets to temperatures of about 100° C.±5° C. for at least two seconds before returning the media sheets to a media transport that carries the sheets through the inkjet printer are explained in the following description, taken in connection with the accompanying drawings.
For a general understanding of the environment for the printer and the printer operational method disclosed herein as well as the details for the printer and the printer operational 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 word “printer” encompasses any apparatus that ejects ink drops onto media to form ink images.
The printer and method described below direct printed sheets into a dryer that moves the printed sheets vertically through the dryer and then places the dried sheets onto a media transport. The vertical structure of the dryer does not require the footprint of the inkjet printer to expand while increasing the dwell time of the printed sheets in the dryer.
The printer 10 is configured to perform print jobs sent to the printer by an external data source. As used in this document, the term “print job” means ink image content data for a series of ink images to be produced by a printer and the print job parameters at which the printer is operated to produce the ink images. The ink image content data is sent to the controller 80 from either an external data source, such as a scanning system or an online or work station connection. The ink image content data is processed to generate the inkjet ejector firing signals delivered to the printheads in the modules 34A-34D. Along with the ink image content data, the controller also receives print job parameters that identify the media weight, media dimensions, print speed, media type, ink area coverage to be produced on each side of each sheet, location of the image to be produced on each side of each sheet, media color, media fiber orientation for fibrous media, print zone temperature and humidity, media moisture content, media manufacturer, and the like for executing a print job. As used in this document, the term “print job parameters” means non-image content data for performing a print job and the term “ink image content data” means digital data that identifies a color and a volume of each ejected ink drop that forms pixels in the ink images to be printed on the media sheets produced by a print job.
In one embodiment, each printhead module of the printer 10 has only one printhead that has a width that corresponds to a width of the widest media in the cross-process direction that can be printed by the printer. In other embodiments, the printhead modules have a plurality of printheads with each printhead having a width that is less than a width of the widest media in the cross-process direction that the printer can print. In these modules, the printheads are arranged in an array of staggered printheads that enables media wider than a single printhead to be printed. Additionally, the printheads within a module or between modules can also be interlaced so the density of the drops ejected by the printheads in the cross-process direction can be greater than the smallest spacing between the inkjets in a printhead in the cross-process direction. Although printer 10 is depicted with only two supplies of media sheets, the printer can be configured with three or more sheet supplies, each containing a different type or size of media.
The media transport 42 includes a belt for moving print media, such as paper sheets, envelopes, or any other article suitable for receiving printed images, through the print zone so the printheads can eject ink drops onto the moving media to form printed images on the media. The belt has holes in it and the belt moves over a vacuum plenum within the conveyor 52 so a suction force can be generated through the surface of the belt. Each print medium engages a portion of the holes on the surface of the belt and the suction force holds the print medium to the surface of the belt to prevent the print media from slipping or otherwise moving relative to the surface of the belt as the belt moves through the printer. Holding each print medium in place relative to the surface of the moving belt enables the printer to control the timing of the operation of printheads to ensure that the printheads form printed images in proper locations on each print medium and ensures that the print media do not cause jams or other mechanical issues with the printer. In large-scale printer configurations, the belt often carries multiple print media simultaneously.
With continued reference to
A return path 72 is provided to receive a sheet from the media transport 42 after a substrate has been completely or partially printed and passed through the dryer 30. The sheet is moved by the rotation of pulleys in a direction opposite to the direction of movement in the process direction past the printheads. An actuator 40 operatively connected to pivot 88 is operated by the controller 80 to either block entry to the return path 72 and direct the media to the receptacle 56 or direct the media to the return path 72. At position 76, the substrates on the return path 72 can either be turned over so they can merge into the job stream being carried by the media transport 42 and the opposite side of the media sheet can be printed or left as they are so the printed side of the sheet can be printed again. To leave the sheets as they are, the controller 80 operates an actuator to turn pivot 82 counterclockwise to the position shown in the figure so the sheets bypass the bend in the return path and are directed to position 76 without being turned over. Thus, the printed side of the sheet can be printed. If the controller 80 operates the actuator to turn pivot 82 clockwise, then the sheet goes over the bend and is flipped before being returned to the transport path 42.
The printer 10 is configured with two optical sensors 84A and 84B. The optical sensor 84A that precedes the print zone in the process direction is used to generate image data of partially printed ink images returned to the media transport 42 for a second pass of the media sheet through the print zone for completion of the ink image. The optical sensor 84B that follows the dryer 30 in the process direction is used to generate image data of completely printed and partially printed ink images that have passed through the dryer. The controller is configured to process the image data from optical sensor 84B to determine whether the heater components in the dryer 30 need to be adjusted. The optical sensors 84A and 84B can be a digital camera, an array of LEDs and photodetectors, or other devices configured to generate image data of a passing surface.
As further shown in
Operation and control of the various subsystems, components and functions of the machine or printer 10 are performed with the aid of a controller or electronic subsystem (ESS) 80. The ESS or controller 80 is operatively connected to the components of the printhead modules 34A-34D (and thus the printheads), the actuators 40, the dryer 30, and the optical sensors 84A and 84B. The ESS or controller 80, for example, is a self-contained computer having a central processor unit (CPU) with electronic data storage, and a display or user interface (UI) 50. The ESS or controller 80, for example, includes a sensor input and control circuit as well as a pixel placement and control circuit. In addition, the CPU reads, captures, prepares, and manages the image content data flow between image input sources, such as a scanning system or an online or a work station connection (not shown), and the printhead modules 34A-34D. As such, the ESS or controller 80 is the main multi-tasking processor for operating and controlling all of the other machine subsystems and functions, including the printing process.
The controller 80 can be implemented with general or specialized programmable processors that execute programmed instructions. The instructions and data required to perform the programmed functions can be stored in non-transitory, computer-readable memory associated with the processors or controllers. The processors, their memories, the instructions and data stored in the memories, and the interface circuitry configure the controllers to perform the operations described below. These components can be provided on a printed circuit card or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits can be implemented with a separate processor or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with discrete components or circuits provided in very large scale integrated (VLSI) circuits. Also, the circuits described herein can be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits.
In operation, ink image content data for an ink image to be produced is sent to the controller 80 from either a scanning system or an online or work station connection. The ink image content data is processed to generate the inkjet ejector firing signals delivered to the printheads in the modules 34A-34D. Along with the ink image content data, the controller receives print job parameters that identify the media weight, media dimensions, print speed, media type, ink area coverage to be produced on each side of each sheet, location of the image to be produced on each side of each sheet, media color, media fiber orientation for fibrous media, print zone temperature and humidity, media moisture content, and media manufacturer.
The conveying mechanism 200 for vertically transporting sheets through the dryer 30 is shown in
As shown in
With reference again to
Prior to process 200 operating the printer 10, the controller determines from the print job parameters a speed for moving the media sheets past the printheads for printing and through the dryer for fixing the ink images on the media (block 204). For example, the type and size of the media affects the drying time. The process 200 operates the actuators 40 to achieve the determined media speed on the media transport and operates the actuators to rotate the belts in the dryer to synchronize the belts in the dryer with the arrival of media sheets at the dryer and achieve the dwell time within the dryer (block 208). The print job is then printed (block 212) and the process repeats for the next print job (block 216).
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 or applications. 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.
