Patent Application
20190056680
This application relates generally to doctor blades on toner-based electro-photographic printers and multifunction peripherals. The application relates more particularly to a plurality of staggered doctor blades for generating a uniform layer of toner on a developer roller 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, a developer roller, and developer. 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 transfers toner from a toner hopper to a sheet of paper where it is fused by heat to the paper.
However, if the toner is not evenly distributed on the developer roller, or is poorly charged, or has the wrong polarity, then toner can inadvertently end up in the wrong place on the printed page, settle as dust on printer parts that could interfere with the proper operation of an electrostatic process unit, or otherwise accumulate as waste.
In an example embodiment, an apparatus includes two or more doctor blades that are configured to distribute a substantially uniform layer of toner onto a developer roller of a toner-based printer such as a laser printer or multifunction peripheral. A first doctor blade reduces the layer of toner to a first depth, and a second doctor blade further reduces the layer of toner to a second depth. A third or subsequent doctor blade further reduces the layer of toner to the desired depth. In a configuration, one or more of the doctor blades have an electrical charge that produces a substantially uniform charged layer of toner on the developer roller.
In an example embodiment, an electrostatic process unit includes a developer roller that attracts an initial layer of toner from a toner hopper, and two or more doctor blades that reduce the initial layer of toner on the developer roller to a substantially uniform desired depth. The electrostatic process unit can include additional structures such as an electrostatic drum, a primary charge roller, a controllable light source such as a semiconductor laser. A first doctor blade reduces the layer of toner to a first depth, and a second doctor blade further reduces the layer of toner to a second depth. A third or subsequent doctor blade further reduces the layer of toner to the desired depth. In a configuration, one or more of the doctor blades have an electrical charge that produces a substantially uniform charged layer of toner on the developer roller.
In an example embodiment, a method of generating a substantially uniform layer of toner on a developer roller includes attracting toner from a toner hopper onto the developer roller and removing toner to a desired depth by two or more doctor blades. The method can include applying an electrical charge to one or more of the doctor blades to produce a substantially uniform charged layer of toner on the developer roll.
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, 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 and fused with 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.
If the toner is poorly charged, or if the toner is the wrong polarity, then toner may not transfer as intended from the magnetic developer roller, to the photoconductive drum, and ultimately to the paper. Stray toner can inadvertently end up on the printed page, settle as dust on printer parts, or otherwise accumulate as waste. The stray toner can interfere with the proper operation of an electrostatic process unit, or EPU, that typically comprises the photoconductive drum, the magnetic developer roller, and developer in a field replaceable unit or a self-contained compact cartridge. Therefore minimizing stray toner can improve the quality of printed images, reduce waste, and lower maintenance costs.
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In a configuration, one or more of the doctor blades 300 can be configured to have a charge. For example, a negative voltage such as a −500 VDC to −1500 VDC charge can be applied to one or more of the staggered doctor blades 300. The application of this charge on the staggered doctor blades 300 induces the correct charge on the toner particles as the toner contacts the staggered doctor blades 300. Charging one or more of the staggered doctor blades 300 advantageously results in the toner on the magnetic developer roller 310 having a more uniform charge, and can correct toner that is not charged correctly or that has the wrong polarity. Advantageously, correctly charged toner that has a uniform charge improves print quality, increases the transfer efficiency of toner from the magnetic developer roller to the photoconductive drum, and from the photoconductive drum to the paper (not shown, see for example
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At process block 402, a developer roller attracts an initial layer of toner from a toner hopper. The developer roller can attract the toner magnetically, electrostatically, or through a combination of magnetic and electrostatic forces. Processing continues to process block 404.
At process block 404, one or more doctor blades optionally receive an electrical charge, for example a charge of between approximately −500 VDC and approximately −1500 VDC. The charge ensures that the toner is uniformly charged after process block 406, 408, and 410. Processing continues to process block 406.
At process block 406, the developer roller rotates the toner towards a first doctor blade that reduces the initial layer of toner to a first desired depth, for example 1.78 mm. If the first doctor blade was charged in process block 404, the first doctor blade will induce a uniform charge on the toner as the toner contacts the first doctor blade. Processing continues to process block 408.
At process block 408, the developer roller continues to rotate the toner towards a second doctor blade that further reduces the toner to a second desired depth, for example 1.54 mm. If the second doctor blade was charged in process block 404, the second doctor blade will induce a uniform charge on the toner as the toner contacts the second doctor blade. Processing continues to process block 412.
At process block 410, the developer roller continues to rotate the toner towards a third doctor blade that further reduces the toner to a third desired depth, for example 1.27 mm. If the third doctor blade was charged in process block 404, the third doctor blade will induce a substantially uniform charge on the toner as the toner contacts the third doctor blade. Processing continues to process block 412.
At process block 412, the developer roller continues to rotate and transfers at least a portion of the toner from the developer roller to a photoconductive drum for printing a desired image. Other printing operations are then performed including transferring the toner from the photoconductive drum to paper, and fusing the toner onto the paper. Processing terminates at end block 414
In light of the foregoing, it should be appreciated that the present disclosure significantly advances the art of toner-based printing. 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.
