Patent Application
20070109383
This disclosure relates generally to printers having an intermediate imaging member and, more particularly, to the components and methods for imaging in ink printers having an intermediate imaging member.
Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are placed in a feed chute and a feed mechanism delivers the solid ink to a heater assembly. Solid ink sticks are either gravity fed or urged by a spring through the feed chute toward a heater plate in the heater assembly. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto a recording medium. U.S. Pat. No. 5,734,402 for a Solid Ink Feed System, issued Mar. 31, 1998 to Rousseau et al. and U.S. Pat. No. 5,861,903 for an Ink Feed System, issued Jan. 19, 1999 to Crawford et al. describe exemplary systems for delivering solid ink sticks into a phase change ink printer.
In known printing systems having an intermediate imaging member, such as ink printing systems, the print process includes an imaging phase, a transfer phase, and an overhead phase. In ink printing systems, the imaging phase is the portion of the print process in which the ink is expelled through the piezoelectric elements comprising the print head in an image pattern onto the image drum or other intermediate imaging member. The transfer or transfix phase is the portion of the print process in which the ink image on the image drum is transferred to the recording medium. The overhead phase is the portion of the print process in which the operation of the intermediate imaging member and the transfer roller are synchronized for transfer of the image from the image drum or intermediate imaging member.
In currently known print processes for ink printing machines, bi-directional rotation of the intermediate imaging member is used for formation of the image on the intermediate imaging member. After the image is formed, the intermediate imaging member is stopped and its direction of rotation is reversed for transfer of the image from the drum. As the leading edge of the image approaches the transfer roller, the transfer roller is engaged to press the recording medium against the intermediate imaging member for transfer of the image from the intermediate imaging member to the recording medium. The intermediate imaging member is rotated more slowly during the transfer phase to transfer the image to the recording medium more efficiently. After the image is transferred and while the recording medium which bears the image is being transported into the output tray, the transfer roller is disengaged and the intermediate imaging member rotation is reversed for a new imaging operation.
In order to print more pages per unit of time, such as a minute, a new print process and apparatus have been developed. A process transfers an image from an intermediate imaging member onto a sheet of recording media while preserving the ability to duplex print on the sheet. The process includes generating an image on an intermediate imaging member as the intermediate imaging member rotates in a first direction, synchronizing a sheet of recording media with the image on the intermediate member as the intermediate imaging member continues to rotate in the first direction, transferring the image from the intermediate imaging member onto the sheet of recording media as the intermediate imaging member continues to rotate in the first direction, and limiting release agent on the intermediate imaging member to a level that preserves duplex printing capability on the sheet of recording media.
An apparatus transfers an image from an intermediate imaging member onto a sheet of recording media. The apparatus includes a print head for generating an image on an intermediate imaging member as the intermediate imaging member rotates in a first direction, a transport synchronizer for synchronizing a sheet of recording media with the image on the intermediate member as the intermediate imaging member continues to rotate in the first direction, a transfer roller for transferring the image from the intermediate imaging member onto the sheet of recording media as the intermediate imaging member continues to rotate in the first direction, and a release agent limiter for limiting release agent on the intermediate imaging member to a level that preserves duplex printing capability on the sheet of recording media.
In an embodiment for the transfer apparatus that may be used in a solid ink jet printer, the transfer apparatus includes an intermediate imaging member for bearing an image, a print head for ejecting ink onto the intermediate imaging member to form an image on the intermediate imaging member as it rotates in a first direction, a sheet synchronizer for synchronizing a sheet of recording media with the image on the intermediate member as the intermediate imaging member continues to rotate in the first direction, a transfer roller for transferring the image from the intermediate imaging member onto the sheet of recording media as the intermediate imaging member continues to rotate in the first direction, a drum maintenance roller for contacting the intermediate imaging member to apply release agent to the intermediate imaging member after the transfer roller has commenced transferring the image to the sheet of recording media, and a release agent blade for removing a portion of the release agent applied to the intermediate imaging member by the drum maintenance roller so the level of release agent on the intermediate imaging member preserves duplex printing on the sheet of recording media.
The foregoing aspects and other features of an ink printer implementing a forward direction printing process are explained in the following description, taken in connection with the accompanying drawings, wherein:
Referring to
In the particular printer shown in
A color printer typically uses four colors of ink (yellow, cyan, magenta, and black). Ink sticks 30 of each color are delivered through a corresponding individual one of the feed channels 28A-D. The operator of the printer exercises care to avoid inserting ink sticks of one color into a feed channel for a different color. Ink sticks may be so saturated with color dye that it may be difficult for a printer user to tell by color alone which color is which. Cyan, magenta, and black ink sticks in particular can be difficult to distinguish visually based on color appearance. The key plate 26 has keyed openings 24A, 24B, 240, 24D to aid the printer user in ensuring that only ink sticks of the proper color are inserted into each feed channel. Each keyed opening 24A, 24B, 240, 24D of the key plate has a unique shape. The ink sticks 30 of the color for that feed channel have a shape corresponding to the shape of the keyed opening. The keyed openings and corresponding ink stick shapes exclude from each ink feed channel ink sticks of all colors except the ink sticks of the proper color for that feed channel.
As shown in
A duplex image includes a first image that is transferred from the intermediate imaging member onto a first side of a recording media sheet followed by a second image that is transferred from the intermediate imaging member onto the reverse side of the recording media sheet to which the first image was transferred. One problem that occurs in printing systems that apply a release agent to the intermediate imaging member is the contamination of the reverse side of a recording media sheet with release agent during the transfer of the first image onto the sheet. This contamination may then generate defects during the transfer of the second image on the reverse side of the recording media sheet. If a duplex image is to be transferred to the reverse side of a sheet, the reverse side of the sheet is presented to the intermediate imaging member by directing the sheet through the duplex print path 68 after it has passed through the transfer roller for the transfer of the first image. As the transfer process is repeated, the second image is transferred from the intermediate imaging member 52 to the reverse side of the sheet imaged during the previous transfer cycle. The sheet bearing the duplex image is then ejected by the ejection rollers 74 and deposited in the output tray 78.
The operations of the ink printer 10 are controlled by the electronics module 44. The electronics module 44 includes a power supply 80, a main board 84 with a controller, memory, and interface components (not shown), a hard drive 88, a power control board 90, and a configuration card 94. The power supply 80 generates various power levels for the various components and subsystems of the ink printer 10. The power control board 90 regulates these power levels. The configuration card contains data in nonvolatile memory that defines the various operating parameters and configurations for the components and subsystems of the ink printer 10. The hard drive stores data used for operating the ink printer and software modules that may be loaded and executed in the memory on the main card 84. The main board 84 includes the controller that operates the ink printer 10 in accordance with the operating program executing in the memory of the main board 84. The controller receives signals from the various components and subsystems of the ink printer 10 through interface components on the main board 84. The controller also generates control signals that are delivered to the components and subsystems through the interface components. These control signals, for example, drive the piezoelectric elements to expel ink through the apertures in the chemically etched print plates to form the image on the imaging member 52 as the member rotates past the print head.
In previously known solid ink printers, the more efficient print process imaged the member 52 as it rotated in a first direction, stopped the member rotation, reversed the member rotation, and then transferred the image from the intermediate imaging member onto the sheet of recording media. This process enabled the transfer roller 76 to be moved to form the nip for transferring the image to the media sheet as the edge of the paper was coming to the nip. This reduced the likelihood that the transfer roller 76 contacted intermediate member 52 and became contaminated with release agent. The directional control of the member rotation was performed by the controller of the main board 84 in accordance with signals generated by the controller. In an effort to obtain greater throughput rates, efforts have been made to perform the imaging and transferring phases as the intermediate member rotated in the same direction to reduce the amount of overhead associated with stopping and reversing the intermediate member 52. These efforts, however, have resulted in the transfer roller 76 contacting the intermediate roller 52 before the edge of the media sheet arrives at the nip between the roller 76 and the imaging member 52. Consequently, release agent is transferred to the transferring roller 76 and this release agent is transferred from the roller 76 to the reverse side of recording media sheets. The release agent may be present on the reverse side of media sheets at levels that degrade the quality of duplex images on the sheet.
In an improved print process, the controller rotates the intermediate imaging member 52 in the same direction for imaging and transferring, but the imaging member is rotated at a faster speed during the imaging phase than it is for the transferring phase. Additionally, the drum maintenance subsystem 54 and the wiper subassembly 60 are operated in a way that reduces the likelihood of release agent contamination of the reverse side of a recording media sheet as it passes between the transfer roller 76 and the intermediate imaging member 52.
The single direction imaging print process is shown in
Approximately a quarter of a revolution after the imaging phase commences (104), the imaging phase of the print process continues as the drum maintenance roller 92 is disengaged so it no longer contacts the intermediate imaging member. If the imaging phase shown in
As the beginning of the imaging area approaches the transfer subsystem on the next revolution following the one in which the image on the imaging member was generated (110), the transfer roller is engaged to contact and form a nip with the imaging member so a sheet of recording media is pressed between the transfer roller and the imaging member. In one embodiment, the transfer roller is sized so that about 6 mm of the imaging member's circumference is pressed within the nip at the transfer roller. As the image is transferred onto the sheet, the controller regulates the surface speed of the transfer roller, the intermediate imaging member, and the sheet of recording media to be substantially equal. In one embodiment, the speed of the imaging member 52 is reduced as it approaches the transfer roller for the transferring of the image onto the sheet of the recording media. In one embodiment, the transfer roller, imaging member, and sheet are maintained at a speed in the range of approximately 15 to approximately 50 inches per second for transferring the image onto the first side of a sheet, and, if an image is transferred on the reverse side, the speed is regulated to be in the range of approximately 5 to approximately 30 inches per second. In order to maintain these speeds, the transfer roller is urged against the intermediate imaging member with known components at pressures of 500 to 1000 psi in the nip region. The transfer roller in one embodiment has a relatively hard inner elastomer layer and a relatively soft outer elastomer layer. Such a roller, for example, has an inner elastomer layer that is approximately 2.2 mm thick with a 64 ShoreD durometer value and an outer elastomer layer that is 0.3 mm thick with a 70 ShoreA durometer value. The transfer roller may, however, have only a single elastomer layer or have more than two elastomer layers.
In this embodiment, an increase in printer productivity is facilitated by interleaving the image transfer and drum maintenance engage and disengage functions. As the trailing end of the media sheet approaches the transfer roller, the drum maintenance roller and wiper blade engage the intermediate member to being applying a layer of release agent for the next sheet. The transfer roller then disengages the intermediate member as the end of the sheet exits the nip at the transfer roller. The drum maintenance roller then continues to apply release agent until an area of the intermediate member that corresponds with the area of a media sheet has release agent applied to it. The drum maintenance roller and the wiper blade disengage from the intermediate member while an image is being formed on the intermediate member. The interleaved motions reduce inefficiencies in the overhead phase of the printing process.
To facilitate separation of the sheet of recording media from the transfer roller after the image is transferred onto the sheet, known components may be provided in the transferring subsystem. These components may include an air knife, stripper fingers, or a stripper blade. In one embodiment, a plastic stripper blade may be actuated so it contacts only the substrate at the lead edge as it leaves the transfer roller nip to facilitate separation.
Additional parameters that may be controlled by an ink printer implementing a single direction print process are the temperatures of the recording media sheets and the imaging member. The imaging member may be heated by placing a heater either in the internal volume of the imaging member or proximate the exterior of the member and monitoring the surface temperature with a sensor placed in proximity to the member. Such heaters are well known and include halogen heaters or inductive heaters. The transfer subsystem may also include a heater for heating the recording media sheets. Such a heater may be a clamshell plate-on-plate heater that is closed for transferring images on a single side of a sheet and opened for the reverse side of sheet subjected to duplex transferring. In one embodiment, the recording media sheet heater is maintained at 65° C. and the imaging member heater is regulated so the temperature of the member remains in the range of approximately 40° C. to approximately 70° C. These temperatures are used as they tend to keep the image ink at a phase that is not so hard that the ink does not adequately adhere to the sheet and not so liquid that the ink shears and leaves a residual layer on the imaging member. Of course, the chemical composition of the ink may alter the optimal temperature or temperature range for the image ink and paper.
After the beginning of the imaging area on the imaging member has passed through the transferring nip and past the print head (114,
Effective release agents include silicone fluids comprised of a blend of an organo-functional silicone oil and a non-functional silicone diluent. The concentrated organo-functional portion reacts with the imaging drum surface coating to improve oil uniformity while the diluent helps determine the overall release agent viscosity. In one embodiment, an amine functional silicone fluid is ued that is comprised of approximately 0.025-0.15 mol % amine and a viscosity of 10-100 cP. In some applications, lower amine levels, such as, 0.025-0.075 mol % amine, and viscosities of 10-30 cP may enhance transferring performance. In one embodiment, a release agent viscosity that is less than 70 cP is used to minimize oil bar size on the intermediate imaging member as discussed in more detail below.
As the end of the imaging area on the imaging member exits the transfer subsystem (118,
As shown in
As may be observed from
Another benefit of the single direction print process is that the imaging member drum speed is greater at drum maintenance roller disengagement. The higher speed is made possible by the disengaging of the maintenance roller from the imaging member after the member has reached the imaging speed. The higher speed of the member when the maintenance roller is released reduces the size of the oil bar at end of the imaging area on the imaging member. In one embodiment, the drum maintenance roller disengages from the intermediate member while the intermediate member is rotating at a surface speed of approximately 50 inches per second or greater (ips). The oil bar is the line of demarcation of release agent that is left on the imaging member as the wiper blade 60 disengages from the intermediate member. The excessive oil in the oil bar may the source of multiple machine difficulties. For example, excess oil in an oil bar may be splattered into machine components, such as the face of the print head. The level of the oil in the oil bar may be great enough that it is transferred to the transfer roller and then one revolution of the transfer roll later transferred to the reverse side of a sheet to which an image is being transferred. If this sheet is subjected to the duplex printing process, the oil on the sheet may be sufficient enough to degrade the image on the second side printed on the sheet. Therefore, a reduction in the oil bar size reduces the likelihood that the oil bar affects the quality of an image transferred to the reverse side of a recording media sheet.
Excessive oil on the reverse side of a recording media sheet may also be reduced by controlling the distance between the disengaging of the maintenance roller and the disengaging of a release agent wiper blade. The release agent wiper blade is typically a pivoting member that reaches across the width of the imaging member. In order to be effective, the imaging member is rotating in a direction so that the surface of the member contacts the maintenance roller before encountering the wiper blade. After the maintenance drum contacts the imaging member and begins to apply release agent oil to the imaging member, the wiper blade is pivoted so its outboard edge contacts the member and removes excess oil from the surface of the member. In one embodiment, the wiper blade is pivoted so it no longer contacts the imaging member after at least 50 mm of the imaging member surface has rotated past the position where the drum maintenance roller disengaged from the member. The delay in pivoting the wiper blade away from the imaging member reduces the oil bar on the imaging member. In one embodiment, the size of the oil bar is reduced by positioning the wiper blade so that the angle at the blade tip at the line touching the imaging member is greater than 60° and the blade holder angle at the last touch of the blade to the member is greater than 80°.
While the printer 10 has been described as implementing the single direction print process, another embodiment of a printer may be constructed that implements two single direction print processes. One single direction print process coordinates the engagement and disengagement of the transfer roller and drum maintenance roller to perform the ‘on the fly’ registration described above. This process may be used for media sheets that are sized to conform to the intermediate member area coverage that is possible during the interleaving of the ‘on the fly’ registration. The other single direction print process performs the intermediate member rotational stop and transfer roller engagement of the media sheet leading edge that reduces the likelihood that the transfer roller picks up release agent from the intermediate member during the transfer phase. The controller may determine from print job parameters which single direction print process is optimal for a print job and use that process for a print job. For example, image printing on recording media sheets that are legal size may be best performed with the process that stops the intermediate member so the transfer roller engages the leading edge of the media sheet without touching the intermediate member. The intermediate member is then accelerated during the transfer phase until the trailing edge of the media sheet approaches the nip. The intermediate member is then stopped before the trailing edge leaves the nip so the transfer roller is disengaged from the intermediate member before the roller contacts the intermediate member. Such a printer enables the printer to have flexibility to perform a wider range of print jobs.
Those skilled in the art will recognize that numerous modifications can be made to the specific implementations described above. Those skilled in the art will recognize that the single direction print process and release agent control may be adapted for other printers using an intermediate imaging member, such as xeroxographic printers or offset lithographic printers. 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.
