Patent Application
20190094785
This application relates generally to cleaner blades on toner-based electro-photographic printers and multifunction peripherals. The application relates more particularly to an electrified cleaner blade for removing residual toner from a photoconductive drum of an electrostatic process unit of a printer.
Document processing devices include printers, copiers, scanners and e-mail gateways. More recently, devices employing two or more of these functions are found in office environments. These devices are referred to as multifunction peripherals (MFPs) or multifunction devices (MFDs). As used herein, MFP means any of the forgoing.
An electrostatic process unit, or EPU, in many printers and multifunction peripherals assists in performing the printing functions. The EPU typically comprises a photoconductive drum, and a developer roller. The EPU can be configured as a field replaceable unit or can be part of a self-contained compact cartridge that includes the toner. Using magnetic and electrostatic forces, the developer roller and the photoconductive drum transfer toner from a toner hopper to a sheet of paper where it is fused by heat to the paper.
After the photoconductive drum transfers toner to the paper, a cleaner blade in the EPU removes residual toner and paper dust from the photoconductive drum. However, if residual toner and paper dust is not entirely removed from the photoconductive drum by the cleaner blade the residual toner and paper dust can degrade future print jobs, cause surface wear on the photoconductive drum, contaminate other EPU components such as the primary charge roller or the corona components and interfere with the proper operation of an electrostatic process unit.
In an example embodiment, an apparatus includes a cleaner blade and an electrostatic charge unit. The cleaner blade is configured to remove residual material from an associated photoconductive drum of a toner-based printer, for example by physically removing material as the drum is rotated towards the cleaner blade and by electrostatically attracting submicron particles from the drum to the cleaner blade. In a configuration, the cleaner blade includes an insulating portion and a conductive or charge carrying portion, where the conductive portion contacts the photoconductive drum. Some or all of the cleaner blade can be made of urethane treated with an ionic salt, urethane to which lithium perchlorate has been added, or treated urethane having an electrical conductivity of between approximately 10 ohm-cm to approximately −5 ohm-cm. The electrostatic charge unit can apply a second electric charge, for example a charge having the reverse polarity than the charge initially applied to the cleaner blade, to remove residual material from the cleaner blade. The cleaner blade can be configured to apply an electric charge to the photoconductive drum.
In an example embodiment, an electrostatic process unit includes a photoconductive drum that selectively attracts toner from a developer roller and deposits the attracted toner onto paper, and an electrified cleaner blade that electrostatically removes residual toner left on the photoconductive drum that was not deposited onto the paper. Some or all of the cleaner blade can be made of urethane treated with an ionic salt, urethane to which lithium perchlorate has been added, or treated urethane having an electrical conductivity of between approximately 10 ohm-cm to approximately −5 ohm-cm. The electrostatic process unit can include a primary charge roller that places a substantially uniform electric charge on the photoconductive drum. The electrified cleaner blade can work in concert with the primary charge roller to apply, for example by placing an initial electric charge on the photoconductive drum. The electrified cleaner blade can include an insulating portion and a conductive portion, where the charge is applied to the conductive portion. The electrostatic process unit can include an electrostatic charge unit for applying the charge to the electrified cleaner blade. The electrostatic charge unit can apply a second electric charge of opposite polarity to remove residual material from the cleaner blade.
In an example embodiment, a method includes placing an electric charge on at least a portion of a cleaner blade and removing, by the cleaner blade and the associated electric charge, residual material from a photoconductive drum of a toner-based print unit. The method can include placing a second electric charge on the cleaner blade to remove material from the cleaner blade. The method can include transferring charge from the cleaner blade to the photoconductive drum to place an electric charge on the photoconductive drum.
The systems and methods disclosed herein are described in detail by way of examples and with reference to the figures. It will be appreciated that modifications to disclosed and described examples, arrangements, configurations, components, elements, apparatuses, devices methods, systems, etc. can suitably be made and may be desired for a specific application. In this disclosure, any identification of specific techniques, arrangements, etc. are either related to a specific example presented or are merely a general description of such a technique, arrangement, etc. Identifications of specific details or examples are not intended to be, and should not be, construed as mandatory or limiting unless specifically designated as such.
In toner-based electro-photographic printers, toner is picked up by a magnetic developer roller from a toner hopper. A precise leveling blade called a doctor blade is positioned close to the magnetic developer roller and removes excess toner to ensure there is only a thin even layer of toner on the magnetic developer roller. The magnetic developer roller rotates towards a photoconductive drum onto which an electric charge has been applied, and toner from the magnetic developer roller is electrostatically attracted to and transferred to the photoconductive drum in accordance with a desired image to be printed. The toner is then transferred from the photoconductive drum to paper and fused with the paper to form a printed page. Residual toner that is left on the photoconductive drum is removed by a cleaner blade or wiper blade into a waste bin. In addition to residual toner, the photoconductive drum can pick up paper dust from the paper. The paper dust can include submicron sized calcium carbonate commonly used in a wide range of papers.
Residual toner and paper dust, if not removed by the cleaner blade, can inadvertently end up on the printed page or settle as dust on printer parts. Dust can potentially interfere with the proper operation of an electrostatic process unit, or EPU, that typically comprises the photoconductive drum, the cleaner blade, the magnetic developer roller, and developer in a field replaceable unit or in a self-contained compact cartridge. Therefore removing residual toner and paper dust can improve the quality of printed images, reduce waste, and lower maintenance costs.
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The electrified cleaner blade 300 is configured to contact with, or be in close proximity to, a photoconductive drum 306. As the photoconductive drum 306 rotates toward the electrified cleaner blade 300, the electrified cleaner blade 300 removes material from the photoconductive drum 306 such as particles 308 of residual toner and dust or other materials picked up from the paper, for example calcium carbonate. In an embodiment, the electrified cleaner blade 300 can be suitably displaced by a small gap from the photoconductive drum 306 so as to not contact the photoconductive drum 306 while remaining close enough to remove substantially all of the particles 308 of toner and paper dust from the photoconductive drum 306. However, typically a cleaner blade is constructed of a flexible non-abrasive material that contacts the photoconductive drum 306 without damaging or causing substantial wear to the photoconductive drum 306.
An electrostatic charge unit, or ECU 310, can apply a suitable charge to the conductive portion 304 of the electrified cleaner blade 300. In a configuration, the ECU 310 can apply a negative voltage of between −100 VDC to −2000 VDC to the conductive portion 304 of the electrified cleaner blade 300. Advantageously, applying a charge to the electrified cleaner blade increases the effectiveness of the electrified cleaner blade 300 by removing submicron particles 308308 from the photoconductive drum 306 that might otherwise escape under the nip of a typical cleaning blade and remain on the photoconductive drum 306. In various configurations, a suitable voltage can be applied to the electrified cleaner blade 300 electrostatically attract or repulse submicron particles 308 in order to remove the particles 308 from the photoconductive drum 300.
One example submicron particle 308 is calcium carbonate which is commonly used in a wide range of papers. When submicron particles or other particles 308 accumulate on charge rollers such as the photoconductive drum 306 or other EPU components, the particles decrease print quality, cause malfunctions, and increase maintenance needs. Therefore, removing particles 308 advantageously improves the operation of toner-based printers.
Particles 308 can also accumulate on the electrified cleaner blade 300, for example on the conductive portion 304 or nip of the electrified cleaner blade 300. Particles 308 can contribute to wear on the photoconductive drum 306 acting as an abrasive on the photoconductive coating, in addition to degrading the ability of the photoconductive coating to hold a charge uniformly. In a configuration, the ECU can reverse the voltage applied to the electrified cleaner blade 300, either periodically or as needed, to electrostatically dislodge accumulated particles 308 from the electrified cleaner blade 300. Dislodged particles 308 fall into an associated waste receptacle for disposal. In a configuration, the ECU 310 can apply a positive voltage of between +100 VDC to +2000 VDC for a short period of time, for example during a non-printing interval, to the conductive portion 304 of the electrified cleaner blade 300 to dislodge any accumulated particles 308. Other suitable ranges of voltages can also be used, for example lower voltages to reduce the possibility of discharge between components. In a configuration the ECU 310 can cycle, or alternate the polarity of, the voltage applied to the electrified cleaner blade 300 between a positive voltage and a negative voltage as part of a cleaning cycle to enhance the dislodging and removal of the toner and paper dust from the electrified cleaner blade 300. For example, the voltage can be cycled at a suitable frequency between approximately 10 cycles per second to approximately 10000 cycles per second for a given number of cycles between approximately 10 cycles to approximately 10000 cycles.
Advantageously, the electrified cleaner blade 300 can charge the photoconductive drum 306, for example by acting as a charge bar to charge the photoconductive drum 306 or by supplementing the charging performed by the primary charge roller or corona components.
With reference to
At process block 402, an electrostatic charge is applied to the cleaner blade. For example, an electrostatic charge unit, or ECU, applies a suitable negative charge to a conductive portion of a cleaner blade, for example a negative voltage of between approximately −100 VDC to approximately −2000 VDC. Processing continues to process block 404.
At process block 404, the photoconductive drum is rotated towards the cleaner blade. Processing continues to process block 406.
At process block 406, residual toner and other particles are removed from the photoconductive drum by the cleaner blade. Larger particles are removed by the physical action of the cleaner blade against the photoconductive drum, while other particles, such as submicron particles, are electrostatically attracted from the photoconductive drum by the charge on the cleaner blade. Processing continues to process block 408.
At process block 408, the polarity of the electrostatic charge applied to the cleaner blade is reversed for a short interval, for example during a period when the printer is not printing pages such as the period between the printing of individual pages. The ECU applies a suitable positive charge to the conductive portion of the cleaner blade, for example a positive voltage of between approximately +100 VDC to approximately +2000 VDC. In a configuration, the ECU can cycle the voltage between positive and negative as part of a cleaning cycle to enhance the dislodging and removal of the toner and paper dust from the cleaner blade. For example, the voltage can be cycled at a suitable frequency between approximately 10 cycles per second to approximately 10000 cycles per second for a given number of cycles between approximately 10 cycles to approximately 10000 cycles. Processing continues to process block 410.
At process block 410, accumulated particles on the cleaner blade are electrostatically dislodged from the cleaner blade by the positive voltage applied to the cleaner blade in process block 408. Dislodged particles fall into a waste receptacle. Processing then returns to process block 402 where the polarity of the charge applied to the cleaner blade is reverted back to a negative charge and the cycle is repeated. Processing can terminate at any suitable block, for example when the printer finishes a print job, when the printer enters a sleep or idle mode, or when the printer is turned off.
In light of the foregoing, it should be appreciated that the present disclosure significantly advances the art of removing residual toner and other particles from the photoconductive drum of a toner-based print unit. While example embodiments of the disclosure have been disclosed in detail herein, it should be appreciated that the disclosure is not limited thereto or thereby inasmuch as variations on the disclosure herein will be readily appreciated by those of ordinary skill in the art. The scope of the application shall be appreciated from the claims that follow.
