Patent Application
20120120171
This disclosure relates generally to phase change ink printers, and in particular to transfix apparatus used in phase change ink printers.
Phase change ink imaging apparatus utilize phase change ink to form images on recording media. These apparatus typically include inkjets configured to eject drops of melted phase change ink using either a direct or an offset printing process. In a direct printing process, the ink is deposited directly onto print media. In an offset printing process, the ink is first deposited onto an imaging drum and then transfixed to print media by a transfix roller. In most previously known devices, the transfix roller is loaded against the surface of the imaging drum to form a nip. Sheets of print media are fed through the nip in synchronization with the ink deposited onto the surface of the drum. A predetermined pressure generated by the rolling contact between the print media and the imaging drum in the nip causes the molten ink to transfer and become fixed (i.e., transfixed) to the print media.
The temperature of the print media is typically required to be elevated to a certain degree upon entering the nip to facilitate the transfix process and promote consistent image quality. The elevated temperature of the media also reduces the pressure requirement for the nip. Most previously known phase change ink imaging devices utilize some form of media preheater to elevate the temperature of the media to a desired degree before the media is fed through the nip. While effective, heaters consume energy and affect the cost of operating a printer. Improving energy efficiency in printer technology is a worthwhile goal, and becomes very significant in view of energy conservation efforts and regulatory requirements.
In accordance with one embodiment of the present disclosure, a phase change ink imaging device includes a media transport configured to transport media along a path and a moving member movable proximate at least a portion of the path. The moving member has an image bearing surface. The imaging device includes at least one printhead configured to form an ink image on the image bearing surface, and an image transfix apparatus having at least one transducer configured to direct mechanical energy toward the path after the ink image has been formed on the image bearing surface.
In another embodiment, a phase change ink imaging apparatus includes a media transport configured to transport media along a path, an image bearing surface configured to move proximate a portion of the path, and at least one printhead is configured to form an ink image on the image bearing surface. At least one motion generator is positioned proximate the portion of the path. The at least one motion generator and the image bearing surface define an image transfer zone through which the portion of the path extends. The at least one motion generator includes piezoelectric transducers configured to impact print media moving along the portion of the path at one or more predetermined frequencies.
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 in this document, the word “printer” refers to any device that generates images on media and includes, but is not necessarily limited to inkjet printers, copiers, facsimile machines, multi-function machines, and the like.
The present disclosure is directed to an image transfix apparatus for use in a phase change inkjet printer having an image bearing surface that moves within the imaging device. The image transfix apparatus is positioned proximate the moving surface and includes at least one motion generator that is spaced apart from the moving image bearing surface to define a gap. As explained below, the motion generator may have at least one ultrasonic transducer that is configured to extend into the gap and then retract to contact or impact the image bearing surface rapidly as the image on the surface moves past the transducer in order to spread the ink on the image bearing surface and to transfer and affix the ink to the print media passing through the gap.
The ultrasonic transducers of the motion generator are configured to extend and retract at one or more predetermined frequencies in or near the ultrasonic frequency range. The ultrasonic motion facilitates a near frictionless passage of the image bearing surface through the gap to negate the need for rolling contact as used in previously known transfix apparatus. In addition, the energy generated by the ultrasonic motion elevates the temperature of both the ink and the image bearing surface. The temperature elevation occurs almost instantly, which may reduce or eliminate the need to preheat the image bearing surface and/or print media. Reducing or eliminating preheating requirements shortens the media warm-up time and allows the printer to be shutdown more frequently. Shutting down the printer reduces the energy expenditure of the printer and lowers the associated costs of operating the printer. In addition, the elevated temperatures reduce the force required to achieve a given amount of ink spread resulting in a further reduction in energy expenditure.
The transfix apparatus, as described herein, may be utilized in both offset and direct printing systems. In an offset printing system, the image bearing surface may be a surface of a rotating member, such as a drum, platen, band, or belt, as depicted in
In systems that utilize an imaging member in the form of a band or belt, an additional motion generator may be positioned to direct ultrasonic action to the inner surface of the belt or band opposite from a first motion generator unit. In this case, the ultrasonic action of the additional motion generator in conjunction with the action of the first motion generator serves to stiffen the belt or band to provide a backing surface to facilitate ink spread and transfix the ink to the print media.
The image bearing surface may also comprise print media. For example, in a direct printing system, ink is deposited directly onto print media. In this case, a transfix apparatus may be utilized to apply ultrasonic action to spread the ink and fix the ink to the media. Motion generators may be positioned on one or both sides of the print media to apply mechanical energy to one or both sides of the print media. A similar setup may be utilized in offset systems in which ink is first deposited onto an imaging member and then transferred to print media from the imaging member where the ink is not fixed to the media during the transfer process.
Imaging applications include printing on various media ranging in porosity and smoothness as well as other properties. For example, news print, paper, transparencies, card stock, packaging material, and the like may be printed using the printing system described in this document. Various ink materials, image receiving media, and imaging applications emphasizing one or more objectives, such as image quality, cost, speed or energy efficiency, would enable or favor one or more specific implementations of motion generator transfix apparatus to facilitate image transfer/transfix.
Referring now to
The ink loader 18 is configured to receive phase change ink in its solid form as blocks of ink 28, referred to as solid ink sticks, and to deliver the ink sticks 28 to a melting assembly 30 that melts the solid ink sticks 28 to a liquid ink suitable for forming images on print media. The ink loader 18 includes feed channels 34 into which the ink sticks 28 are inserted. Although a single feed channel 34 is visible in
The melted ink is received in a melt reservoir 44 and then supplied to at least one printhead 48. The printhead 48 includes inkjets configured to eject drops of melted ink. The printer 10 is an offset printer. Accordingly, the printhead 48 is positioned to direct the ink onto an image bearing surface 50 of a rotating imaging member 54. The imaging member 54 comprises a rotating drum, endless belt, band, or similar type of structure. A layer or film of release agent may be applied to the image bearing surface 50 by a release agent application assembly 58 to facilitate the transfer of ink images from the surface 50 to print media 60. In alternative embodiments, the printhead 48 may be positioned to direct the ink directly onto print media.
A media supply and handling apparatus 24 transports print media along a media path 64 defined in the printer 10 that guides print media 60 toward the image bearing surface 50 in synchronization with ink deposited onto the surface 50 by the inkjet printing mechanism 48. The media supply and handling apparatus 24 has at least one media source 68, such as a supply tray, for storing and supplying print media, such as paper, transparencies, or the like. The media supply and handling apparatus includes rollers, baffles, deflectors, and the like for transporting media along the media path 64.
Media conditioning devices may be positioned along the media path 64 for controlling and regulating the temperature of the print media so that the media arrives at the transfix apparatus 100 at a suitable temperature to receive the ink from the image bearing surface 50. For example, in the embodiment of
Operation and control of the various apparatus, components and functions of the printer 10 are performed with the aid of a control apparatus 74. The control apparatus 74 includes a controller 78, electronic storage or memory 80, and a user interface (UI) 84. The controller 78 may comprise a processing device, such as a central processing unit (CPU), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) device, or microcontroller, configured to execute instructions stored in the memory 80. Multiple processors may be used. Any suitable type of memory or electronic storage may be used. For example, the memory 80 may be a non-volatile memory, such as read only memory (ROM), or a programmable non-volatile memory, such as EEPROM or flash memory. During operation, the controller 78 actuates the inkjet printing apparatus 48 to eject drops of ink onto the image bearing surface 50 to form images. The media supply and handling apparatus 24 in turn is activated to transport a sheet of print media 60 along the media path 64 toward the image bearing surface 50.
In the embodiment of
Referring to
A plurality of ultrasonic transducers 118 is incorporated into the front surface 112 of the ultrasonic mechanism 114, as depicted in
Multiple pulse force impacts may be required across each pixel to facilitate the image transfix process, although in some applications a single impact may be sufficient. The rate and frequency of movement of the ultrasonic transducers 118 with respect to the image bearing surface is controlled to achieve a desired number of impacts across each pixel of the ink image as the image bearing surface and print media are moving through the transfix zone 104 at product throughput speeds. In one embodiment, the ultrasonic transducers are actuated at an operating frequency in the ultrasonic range between approximately 15 kHz and 200 kHz. Operating frequencies in the ultrasonic range enable multiple impacts to each pixel to be achieved. The ultrasonic motion also provides the added benefit of generating heat in the transfix zone 104 that facilitates the transfix process. The operating frequency generated by the motion generator units, however, may be any frequency that enables the ultrasonic transducers 118 to contact and withdraw from the moving print media and/or image receiving surface without substantially interfering with the transfix process or the throughput speed of the imaging apparatus, and that accomplishes sufficient image transfer or transfix to a receiving medium.
In the embodiment of
Any number of ultrasonic transducers 118 and arrays of transducers 118 may be used in order to impart a suitable number of impacts to each ink droplet (through the print media) on the image bearing surface. For example, multiple arrays may be incorporated into a single motion generator unit 108. Alternatively, multiple motion generator units 108 may be utilized with each unit having one or more arrays of ultrasonic transducers. The front surface 112 of the ultrasonic mechanism 114 of a unit 108 may be shaped to conform the contour of the image bearing surface 50 in the transfix zone 104 so that multiple arrays of ultrasonic transducers 118 may each be positioned approximately the same distance D from the surface 50. The conformable configuration may be a somewhat matching curvature or a series of flats or near flats set at incremental angles to approximate a drum curvature. The number of elements and arrays is based on attaining a full line of contact coverage over the width of the image area.
In the embodiment of
In the embodiment of
In the embodiment of
The first motion generator unit 108a is configured to impact the media in the transfix zone 104 at a first predetermined frequency, and the motion generator unit 108b is configured to impact the inner surface 134 of the imaging member 54 in matching phase or at a second predetermined frequency that may be the same as or different than the first predetermined frequency where impacts may or may not be phased. In the embodiment of
The transfix apparatus described above should be distinguished from the vibratory devices used in toner printing systems. In those systems, vibrations at a resonant frequency are delivered only to the side of an image bearing surface that is opposite the image. The vibrations are intended to overcome electrostatic attraction of toner particles to the image bearing surface to facilitate the release of the toner particles to media. The transfix apparatus described above operates on the media to press the media into the ink on the image bearing surface. This action both provides localized heating of the media and helps spread the ink while facilitating the transfer of the ink to the media. The motion generators of the transfix apparatus when placed on the side of the image bearing surface opposite the image help heat the ink on the image bearing surface that may have cooled since being ejected from the printhead. Thus, the transfix apparatus described above operates differently on different components of the imaging process than the vibratory devices of toner imaging systems.
It will be appreciated that variations 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 of ordinary skill in the art, which are also intended to be encompassed by the following claims.
