Patent Application
20080095560
Media feed 26 comprises a mechanism configured to engage a sheet 22 of media so as to move the sheet 22 from input 24 to printing device 28 and subsequently from printing device 28 to fuser 30. In one embodiment, media feed 26 comprises an arrangement of one or more rollers or one or more belts driven by one or more motors and associated transmissions. In another embodiment, media feed 26 may comprise a drum or cylinder against which sheet 22 is held and moved to printing device 28. In other embodiments, media feed 26 may comprise other mechanism or structures configured to move sheets 22 from input 24 in a feed direction along a media feed path as indicated by arrow 42. In still other embodiments, media feed 26 may additionally be configured to overturn sheets 22 of media after one side of such sheets is printed upon and return such sheets 22 back to printing device 28 for duplex printing.
Printing device 28 comprises an arrangement of elements or components configured to deposit and pattern printing material upon sheet 22 to form a printed image upon sheet 22. In the particular about illustrated, printing device 28 comprises an electrophotographic printing device generally including drum 46, motor 48, charger 50, imager 52, developer 54 and charger eraser 56. Drum 46 comprises a cylinder configured to be rotatably driven about axis 49 by motor 48 and having an imaging surface 60 configured to selectively retain a pattern or image of electrostatic charge. In particular, surface 60 is configured to be electrostatically charged and to be selectively discharged upon receiving light from imager 52. Although surface 60 is illustrated as being supported by drum 46, surface 60 may alternatively be provided as part of an endless belt supported by a plurality of rollers. In such embodiments, the exterior surface of the endless belt may be configured to be electrostatically charged and to be selectively discharged for creating an electrostatic field in the form of an image. In yet other embodiments, surface 60 may alternatively include an array of individually chargeable pixel electrodes, wherein each pixel electrodes is independently and selectively chargeable to form an electrostatic field in the form of an image upon surface 60. In still other embodiments, an electrostatic field in the form of an image may be formed upon surface 60 with an electrostatic field emitting device located in close proximity to surface 60 such that the device creates a pattern of electrostatic fields across surface 60.
Charger 50 comprises a device configured to electrostatically charge surface 60. In one embodiment, charger 60 includes a corotron or scorotron. In other embodiments, other devices for electrostatic charging surface 60 may be employed.
Imager 52 comprises a device configured to direct a light upon surface 60 so as to form an image. In the example shown, imager 52 comprises a scanning laser which is moved across surface 60 along scan lines as drum 28 is rotated about axis 49. Those portions of surface 60 which are impinged by the light or laser beam 62 become electrically conductive and discharge elect static charge to form an image (or latent image) upon surface 60.
Although imager 52 is illustrated and described as comprising a scanning laser, imager 52 may alternatively comprise other devices configured to selectively emit or selectively allow light to impinge upon surface 60. For example, in other embodiments, imager 52 may alternatively include one or more shutter devices which employed liquid crystal materials to selectively block light and to selectively allow light to pass through to surface 60. In other embodiments, imager 52 may alternatively include shutters which include individual micro or nano light blocking shutters which pivot, slide or otherwise physically move between light blocking and light transmitting states. In those embodiments where surface 60 alternatively comprises an electrophotographic surface including an array of individual pixel electrodes configured to be selectively charged or selectively discharged using an array of switching mechanisms such as transistors or metal-insulator-metal (MIM) devices, charger 50 and imager 52 may be omitted.
Developer 54 comprising device configured to deposit printing material upon surface 60. In one embodiment, developer 54 is configured to deposit electrostatically charged dry toner upon surface 60. In yet another embodiment, developer 54 may be configured to deposit electrostatically charged liquid toner upon surface 60. In yet other embodiments, developer 54 may be configured to deposit or apply other forms of printing material upon surface 60. The electrostatically charged printing material is attracted to or repelled from selected electrostatically charged portions of a surface 60 to form a corresponding pattern or image of printing material upon surface 60. This pattern or image of printing material is subsequently transferred from surface 60 to sheet 22 either directly (as seen in
Charge eraser 56 comprises a device situated along surface 60 and configured to remove residual charge from surface 60. In one embodiment, charger eraser 56 may comprise an LED erase lamp. In other embodiments, charge eraser 56 may comprise other devices or may be omitted.
Fuser 30 comprises a device configured to fuse or more permanently adhere the printing material to sheet 22. In particular, fuser 30 applies heat and pressure to the printing material upon sheet 22 to fuse the printing material to sheet 22 prior to the sheet being discharged to output 32. Depending upon the printing material employed, fuser 30 may comprise various devices. In some embodiments, fuser 30 may be omitted.
Output 32 comprises one more structures configured to provide access to completed or printed upon sheets 22. Output 32 may comprise one ore more trays, bins and the like.
In operation, charger 50 forms a blanket of electrostatic charge across surface 60. Imager 52 selectively radiates surface 62 selectively discharged portions of surface 60 to form an electrostatic image. Developer 54 applies printing material which is selectively attracted or repelled from portions of surface 60 based upon the image of electrostatic fields. For example, in the embodiment illustrated, the printing material applied by developer 54 has the same polarity of charge as surface 60 such that those portions of surface 60 discharged as a result of being irradiated or exposed by imager 52 attract such as toner, having an opposite charge to the charge of surface 60, wherein imager 52 radiates or exposes surface 62 discharged portions of surface 60 where printing material or toner is not desired. Rotation of drum 46 moves the image of printing material into contact or close proximity with sheets 22 carried by media feed 26. Once the image of printing material has been transferred and applied to sheet 22, media feed 26 transfers sheet 22 to fuser 30 which more permanently adheres the printing material to sheet 22. The printed upon sheet 22 is then discharged to output 32. During transport of sheet 22 from input 24 to printing device 28, sheets 22 may become skewed with respect to feed direction 42. This may be the result of many and various factors, including, but not limed to, sheets 22 being fed at a skewed angle, by pick rollers, belts or other components of media feed 26 applying uneven forces to sheet 22 or by sheet 22 itself having edges that are skewed with respect to one another.
Sensors 34 and 36 comprise sensing devices configured to sense and detect skew of sheet 22. In particular, sensors 34 and 36 are configured to detect skew of sheet 22 as sheet 22 is being moved towards printing device 28 by media feed 26. Sensors 34 and 36 are located to sense portions of sheet 22 being transported or moved towards printing device 20 such that signals indicating the detected skew of a portion of sheet 22 are transmitted to controller 38 in a timely manner such that controller 38 may adjust operation of imager 52 to account for the detected skew of the sensed portions of sheet 22 prior to the formation of the electrostatic image upon those portions of surface 60 which will subsequently carry and transfer the printing material to the corresponding sensed portions of sheet 22. At the same time, sensors 34 and 36 are otherwise located as close as possible to printing device 28 so as to minimize the extent to which the skew of the sensed portions of sheet 22 may change from the time such portions are sensed by sensors 34 and 36 and the time at which printing material is applied to such portions of sheet 22. In the example embodiment illustrated, the positioning of sensors 34 and 36 is dependent upon the speed at which sheets 22 are being moved, the rate or speed at which surface 60 is being moved (a diameter of drum 46 and the speed at which drum 46 is rotated), the relative positioning of imager 52 to where printing material is transferred from surface 60 sheets 22 and the time it takes controller 38 to adjust operation of imager 52. As will be described in more detail hereafter, sensors 34 and 36 sense opposite side edges of sheet 22 and transmit signals indicating the determined skew of sheet 22 to controller 28. Although printer 20 is illustrated as including two sensors 32, 34, and other embodiments, printer 20 may alternatively have greater of fewer of such sensors.
Accordingly to one embodiment, sensors 34 and 36 may comprise light emitters and associated light detectors. In such embodiments, light emitted by such light emitters reflects differently off of sheet 22 as compared to an underlying surface behind the sheet 22. The different reflection of light is detected by the light detectors and determined skew. In yet another embodiment, sensor 34 and 36 may comprise optical cameras. In still other embodiments, sensors 34 and 36 may comprise structures which contact side edges 74 and 76 without altering positioning of edges 74 and 76 to determine skew of sheet 22.
Controller 28 comprises a processing unit configured to generate control signals which direct the operation of media feed 26, motor 48, charger 50, imager 52, developer 54, charge eraser 56, fuser 30 and sensors 34, 36. Based upon signals received from sensors 34 and 36, controller 38 further calculates adjustments and based on such adjustments generates control signals directing imager 52 to reposition the electrostatic image being formed by imager 52 upon surface 60. For purposes of this application, the term “processing unit” shall mean a presently developed or future developed processing unit that executes sequences of instructions contained in a memory. Execution of the sequences of instructions causes the processing unit to perform steps such as generating control signals. The instructions may be loaded in a random access memory (RAM) for execution by the processing unit from a read only memory (ROM), a mass storage device, or some other persistent storage. In other embodiments, hard wired circuitry may be used in place of or in combination with software instructions to implement the functions described. For example, controller 38 may be embodied as part of one or more application-specific integrated circuits (ASICs). Unless otherwise specifically noted, the controller is not limited to any specific combination of hardware circuitry and software, nor to any particular source for the instructions executed by the processing unit.
Although controller 38 is illustrated and described as controlling the operation of media feed 26, fuser 30 or thirty and each of the components of printing device 28, in other embodiments, controller 38 may direct the operation of fewer of such components, wherein additional controllers are provided. For example, in one embodiment, controller 38 may alternatively be associated solely with sensors 34 and 36, wherein controller 38 generates control signals controlling imager 52 based on the image to be formed and the sensed skew of sheet 22.
In addition to sensing side edges 74 and 76, sensors 34 and 36 may additionally sense leading edge 70 and trailing edge 72 as sheet 22 is moved in feed direction 42. Sensors 34 and 36 are arranged such that sides 74 and 76 are within sensing areas 134 and 136, respectively, even when sheet 22 is skewed. According to one embodiment, sensors 34 and 36 continuously sense slide edges 74 and 76 as sheet 22 is moved in feed direction 42. In other embodiments, sensors 34, 36 may alternatively be configured to periodically or intermittently sense spaced portions of side edges 74 and 76.
Because sensors 34 and 36 sense multiple portions of side edges 74 and 76. Sensors 74 and 76 may track paper grain to detect relative movement of sheet 22 a long sides 74 and 76 and to detect changes in skew of sheet 22 while sheet 22 is being fed by media feed 26. For example,
Because printer 20 includes a pair of sensors 34 and 36 sensing opposite side edges as well as the top or leading edge 70 of sheet 22, controller 38 may also detect a width of sheet 22 and potentially the type of media of sheet 22 for each sheet 22 being printed upon and as each sheet is being moved through printer 20. In addition, because printer includes sensors 34 and 36 which sense opposite side edges 74 and 76 of sheet 22, controller 38 may also determine the dimensions and shape of sheet 22. For example, controller 38 may determine whether leading edge 70 is not substantially perpendicular to side edges 74 and 76 or whether trailing edge 72 is not substantially perpendicular to one or both of side edges 74 and 76 from signals provided by such sensors. Such information may be used by controller 38 in its generation of control signals for directing the operation of printer 22 correct or compensate for any changes in shape or size of sheet 22. In other embodiments, printer 20 may alternatively be provided with one or more sensor arranged so as to sense one of side edges 74 or 76 without sensing the other of the side edges 74 and 76.
However, as shown by
Although
In one embodiment, orthogonality of the resulting skewed image on the skewed paper is further enhanced by adjusting for the skewed left and right margins of the image being printed on the sheet. In particular, controller 38 starts particular image line slightly earlier or extends particular image lines slightly farther to accommodate for such skew. In some embodiments, lines can be started a fraction of a dot earlier or later as desired, causing all dots (pixels) on the image line to be slightly shifted. For example, if the image is being rotated clockwise, image lines above a midpoint of sheet 22 are shifted to the right while image lines below the midpoint of sheet 22 are shifted to the left. Adjustments for rotation of the image in a counterclockwise direction any made in an opposite fashion.
As shown by
The location of dots 180 relative to adjacent scan lines 174 and 176 is dependent upon the relative contribution of exposures 184 and 186 to the combined intermediate exposure overlap. For example, where it is desired that a dot 180 to be equidistantly located between scan lines 174 and 176, the intensity or duration of the overlapping exposures 184, 186 are controlled so as to be substantially equal. As shown by
Although the present disclosure has been described with reference to example embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the claimed subject matter. For example, although different example embodiments may have been described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example embodiments or in other alternative embodiments. Because the technology of the present disclosure is relatively complex, not all changes in the technology are foreseeable. The present disclosure described with reference to the example embodiments and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements.
