Patent Application
20110221841
This disclosure relates generally to printers having a drum and, more particularly, to the components for facilitating removal of media from an offset imaging member after the media has passed through a transfix nip.
In known printing systems having a drum, the print process includes an imaging phase, a transfix 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 from the print head in an image pattern onto a transfer imaging surface or drum or other intermediate imaging member. The transfix phase is the portion of the print process in which the ink image is transferred from the drum to the recording medium. The image transfer typically occurs by bringing a transfix roller into contact with the imaging member to form a nip. The surface that is initially imaged may be referred to as a drum or receiving member and may be in the form of a drum, platen, band or the like. These surfaces may be referred to, for convenience, as an imaging drum, imaging member, or more simply, as a drum. The drum typically has a very thin release film on its surface that historically has been referred to as an intermediate transfer layer. This intermediate transfer layer receives the image and permits a more complete transfer of the image to media. A recording medium arrives at the nip as the drum rotates the image through the nip. The pressure in the nip helps transfer the image formed of malleable inks from the drum to the recording medium. As part of the overhead phase, the trailing edge of the recording medium passes out of the nip and the transfix roller is released from contacting the drum. The removal of the transfix member helps release the media from the drum. In some intermediate imaging printers, a stripper blade may be moved into position to intervene between the leading edge of a media leaving the transfix nip and the drum to facilitate separation of the media from the drum.
Inkjet printers that use drums, sometimes called offset printers, have been developed with higher throughput rates. Some of these printers have drum that have larger circumferences than previously known printers. The curvature of a larger drum and the speed of the drum in higher throughput printers reduce the window of time available for moving the stripper blade into position for separation of the media from the drum. As this window of time decreases, the time for the ink on the media to cool after passing through the transfix nip also decreases. Consequently, some portion of the malleable ink may transfer to the stripper blade. Accumulation of this ink on the stripper blade may interfere with the effectiveness of the stripper blade to lift media from the drum. The use of wider media also presents greater challenges in constructing a blade that is sufficiently straight and rigid to establish full strip edge contact across the length. Additionally, at higher rotational speeds the contact between a stripper blade and the drum has resulted in a greater likelihood of damage to the drum's surface. A system that separates media from a drum while preserving the quality of the ink image on each media sheet as well as the surface of the drum benefits the field of offset printing.
A stripper blade has been developed for high throughput inkjet printers. The stripper blade includes a metallic blade body having a first thickness that extends to a leading edge having a second thickness that is less than about 25% of the first thickness, and at least one beveled surface leading from the metallic blade body to the leading edge to form a stripping edge that facilitates separation of media from a drum.
A printer uses the stripper blade described above to facilitate the separation of media from the intermediate imaging member after the media exits a nip formed between the intermediate imaging member and a transfix roller. The printer includes a drum rotating past at least one printhead to receive ink ejected from the at least one printhead, a transfix roller configured to engage the drum selectively to form a nip through which media is transported to receive ink from the drum, and a stripper blade having metallic blade body with a first thickness that extends to a leading edge having a second thickness that is less than about 25% of the first thickness, at least one beveled surface leading from the metallic blade body to the leading edge, and the stripper blade being configured to engage the drum with the leading edge at a position near the nip formed between the transfix roller and the drum to facilitate separation of the media exiting the nip from the drum.
The foregoing aspects and other features of an ink printer implementing a stripper blade system are explained in the following description, taken in connection with the accompanying drawings, wherein:
Referring to
As shown in
A drum heater is controlled by a controller to maintain the drum within an optimal temperature range for generating an ink image and transferring it to a sheet of recording media. A sheet of recording media is removed from the paper/media tray 48 and directed into the paper pre-heater 64 so the sheet of recording media is heated to a more optimal temperature for receiving the ink image. The sheet of recording media is synchronized so its movement between the transfix roller in the transfer subsystem 58 and the intermediate image member or drum 52 is coordinated for the transfer of the image from the imaging member to the sheet of recording media.
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 is configured in accordance with an 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 from the print heads to form the image on the imaging member 52 as the member rotates past the print head. The printer depicted in
The actuator 128 and transfix roller actuator 156 are both configured to operate in response to signals received from a controller (not shown). The controller may be a general purpose microprocessor that executes programmed instructions that are stored in a memory. The controller also includes the interface and input/output (I/O) components for receiving status signals from the printer and supplying control signals to the printer components. Alternatively, the controller may be a dedicated processor on a substrate with the necessary memory, interface, and I/O components also provided on the substrate. Such devices are sometimes known as application specific integrated circuits (ASIC). The controller may also be implemented with appropriately configured discrete electronic components or primarily as a computer program or as a combination of appropriately configured hardware and software components.
A cross sectional view of a stripper blade that may be used to strip media away from an imaging member is depicted in
A detailed view of the leading edge of stripper blade 100 is depicted in
A surface of the stripper blade from
An alternative embodiment of a stripper blade is depicted in
A stripper blade stripping a media sheet from a drum is depicted in
In operation, ink is ejected from at least one print head onto the surface of the drum, forming a latent image. The transfix roller is moved into a transfix nip position with the drum, and the drum rotates, carrying a media sheet through the transfix nip to transfer the latent image from the drum to the media sheet. The stripper blade is placed against the surface of the drum at a position ahead of the leading edge of the media sheet after the leading edge of the media sheet emerges from the transfix nip. At least a portion of the media sheet surface that was in contact with the drum contacts the stripper blade as the media sheet separates from the drum. The portion of the media sheet contacting the stripper blade contacts the stripper blade's low-friction coating. The stripper blade is removed from contact with the drum after the media sheet has separated from the drum. The transfix roller is removed from the transfix nip after the media sheet has passed through the transfix nip. The process recited above may be repeated for multiple media sheets in a printer and may vary to some extent as to phasing or timing of the process.
It will be appreciated that various 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.
