Systems and methods herein generally relate to devices that transport and align sheets, and more particularly to sheet registration methods and devices that have a rotatable frame.
Many machines utilize sheet transports (belts, rollers, etc.) to feed sheets from one processing element to another. For example, it is common for printing devices to transport cut sheets of print media from a web of material or a storage area to a marking engine to allow printing to occur on such sheets of print media. Various factors can contribute to causing sheets to become misaligned when using such transport devices, which can result in defects, such as skewed printing.
Therefore, systems have been developed to maintain alignment between the transport devices and the sheets being transported. For example, physical guides that contact the edges of the sheets can be used to keep the sheets aligned. Other systems utilize sensors, such as optical sensors, physical contact sensors, etc., to detect whether the sheets of media are properly aligned with (registered with) the desired location on the transport devices. Once the amount of misalignment (commonly referred to as skew) is found by the sensors, different corrective measures can be taken to realign (re-register) the sheet with the transport devices. In one example, rollers that form transport nips can be rotated at different speeds (while multiple nips simultaneously contact the skewed sheet) to remove the skew and register the sheet properly. However, such systems can place stresses on the sheets, which can damage sheets; and such systems may not work effectively if the nips cannot properly grip the sheets.
Various alignment devices herein can be used with machines that transport and align sheets, such as printers and similar devices. Exemplary alignment methodologies herein transport a sheet in a processing direction onto a rotatable transport. Such methods determine the amount of rotation of the sheet relative to the processing direction and, after all of the sheet is on the rotatable transport, these methods rotate, in a reverse rotation relative to the direction of skew, the transport by the amount of rotation of the sheet (potentially using just a single actuator) to place the rotatable transport in a compensating rotated position. The rotation of the transport is relative to the fixed-position marking transport. Thus, the sheet is un-rotated relative to the processing direction when the rotatable transport is in the compensating rotated position.
These methods also transport the sheet using the rotatable transport, in the compensating rotated position, to transport the sheet to a marking transport. Note that skew is only corrected by the compensating rotated position of the rotatable transport, and that the drive nips of the rotatable transport all rotate at the same rate, which avoids issues that occur when correcting rotational skew with different nip speeds. Such methods further determine the amount the sheet (e.g., the midline of the sheet) is laterally offset from an alignment position of the marking transport.
Methods herein transport the sheet using the marking transport to a marking engine and print marks on the sheet using the marking engine. These methods print marks on the sheet using the marking engine by laterally offsetting the printing marks an amount equal to the amount the sheet is laterally offset from the alignment position of the marking transport. The amount the midline of the sheet is laterally offset from the alignment position of the marking transport (and the laterally offsetting process) are in a cross-process direction that is perpendicular to the processing direction.
Exemplary alignment apparatuses herein include (among other components), a frame (e.g., rectangular frame), and contact elements, such as rollers that form drive nips, vacuum belts, etc. The contact elements are operatively (meaning directly or indirectly) connected to, and supported by, the frame. The contact elements are shaped and positioned to contact items (such as sheets of print media) that are to be transported in the processing direction relative to the frame. Also, the contact elements are in permanent fixed positions relative to the frame, and do not move relative to the frame. The contact elements are moveable (e.g., rotatable, etc.) at such fixed positions, so as to move the items in the processing direction.
Additionally, such exemplary alignment apparatuses include adjustable mounts (such as actuators, etc.) connected to the frame. The adjustable mounts are connected to the frame in locations (such as corners of a rectangular frame) that cause the adjustable mounts to move the frame in the processing direction and in a cross-processing direction (that is perpendicular to the processing direction). Thus, the adjustable mounts include first adjustable mounts that are positioned to move the frame in the cross-processing direction, and second adjustable mounts that are positioned to move the frame in the processing direction. A controller is electrically connected to the adjustable mounts. In addition, such structures include a sensor electrically connected to the controller. The sensor is positioned to detect the alignment of the items relative to the processing direction.
The controller is adapted to independently control the adjustable mounts to simultaneously rotate the frame and all the contact elements in a clockwise rotation or a counter-clockwise rotation. Also, the controller is adapted to synchronously control the adjustable mounts to simultaneously move the frame and all the contact elements in a cross-processing direction and the processing direction. In other words, the controller is adapted to control the adjustable mounts to simultaneously rotate the frame while moving the frame in the processing direction and the cross-processing direction; therefore, the controller can cause the frame to rotate, while simultaneously moving the frame outboard or inboard, and while advancing or retarding the frame in the processing direction.
Some structures herein include a secondary frame that is positioned within a perimeter of the aforementioned frame (which is sometimes referred to herein as the primary frame). In such structures, secondary contact elements are operatively connected to the secondary frame. Such secondary contact elements are shaped and positioned to similarly contact the items being transported in the processing direction. Similarly, the secondary contact elements are in secondary fixed positions relative to the secondary frame, and the secondary contact elements are moveable (e.g., rotatable) at such secondary fixed positions to move the items in the processing direction.
Also, such alternative structures include secondary adjustable mounts that are connected to the secondary frame and the primary frame, wherein the secondary adjustable mounts are connected to the secondary frame in locations to move the secondary frame parallel to the processing direction of the frame. The secondary adjustable mounts are also electrically connected to the controller, and the controller is similarly adapted to control the secondary adjustable mounts to move the secondary frame parallel to the processing direction of the frame while simultaneously rotating the primary frame and moving the primary frame in the cross-processing direction.
These and other features are described in, or are apparent from, the following detailed description.
Various exemplary systems and methods are described in detail below, with reference to the attached drawing figures, in which:
As mentioned above, registration systems that unevenly rotate drive nips can place stresses on the sheets, which can damage sheets; and such systems may not work effectively if the nips cannot properly grip the sheets. In one specific example, multiple (e.g., 3) nips are sometimes used to provide different nip stance offsets depending on the paper cross-process width. In such systems, the two outside nips are used for wide sheets, while one outside nip and the center nip together are used for more narrow sheets, to handle the different moments wide and narrow sheets present.
One issue with such systems is that the smallest stance needed to handle very small sheets (e.g., 7″ paper) can adversely affect large sheet registration, and this is due to the force/moment balance created as a result of the nips being so close together and offset to one side of the sheet. In such situations, both the inertia of the sheet and the frictional forces on the sheet act through the centerline or center of gravity (CG) of the sheet, which is offset by the distance to the registration nips. Heavy-weight large/wide sheets present high inertial loads at the registration nips which lead to slip and degrade registration performance.
In view of such issues, devices herein separate the overall TOP (Image-on-Paper) registration process into its individual components of “de-skew” and “lateral” registration, and correct each using separate processing rather than using nip steering to perform both functions. With devices herein, the sheet “de-skew” process is started by first measuring the incoming skew (rotation from parallel to the processing direction) of the sheet as it enters the “de-skew” transport. This sheet “de-skew” transport is located immediately upstream of the marking transport.
The sheet “de-skew” transport has a series of drive rollers in arrangement similar to the rest of the machine paper path (e.g., 3 rollers across the process direction, spaced to accommodate all media sizes). The drive rollers and their drive mechanisms are all attached to a common sub-frame, and are square to that sub-frame. The sub-frame pivots about a point (relative to the machine frame) on the upstream end of the “de-skew” transport (allowing the entire module to swing the downstream end either towards the outboard (OB) or inboard (IB) end of the machine). Since the sheet “de-skew” does not occur using nip steering within the module (nip steering adjusts roller speeds differently to steer the sheet) the sheet inertial forces are not an issue when sheets of extended length or width are processed (in the devices herein all rollers feed (rotate) at the same speed).
Using the initial sheet skew measurement, and after allowing the sheet to be controlled entirely by the nips on the “de-skew” transport, the process of articulating the sub-frame is performed. The processor determines the amount to skew the sub-frame relative to the machine frame in order to de-skew the sheet relative to the marking transport. By using this processing, the sheet is delivered to the marking transport in a “de-skewed” orientation, but is not yet corrected for the “lateral” shift of the image relative to the sheet. After the sheet is delivered to the marking transport, the sub-frame can be re-centered, and then adjusted to de-skew the next sheet.
The TOP “lateral” adjustment occurs in the image path. The digital image itself (on a sheet-by-sheet basis) is corrected for the measured “lateral” shift of the sheet relative to the desired position on the sheet. This is performed because the image processing bandwidth needed to “de-skew” an image is very large. However, taking the image and “laterally” shifting the whole image over a certain number of pixels does not require as much computational bandwidth. In this way, both the “de-skew” and the “lateral” registration are corrected in a way that requires simple mechanism (potentially a single actuator for de-skew) and low processing bandwidth for the lateral shift.
Note that the controller/processor 224 (discussed below) and connections thereto are only shown in
As shown in
These methods also transport the sheet of print media 150 using the rotatable transport 100, in the compensating rotated position, to transport the sheet of print media 150 to a marking transport 154 (which is a belt, rollers, etc.). Note that the rotational skew is only corrected by the compensating rotated position of the rotatable transport 100, and that the drive nips 104 supported by axles 102 of the rotatable transport 100 all rotate at the same rate, which avoids issues that occur when correcting rotational skew with different nip speeds. As shown in
The amount of lateral offset (D) can be determined by making calculations from the initial sheet position measured by the skew sensor 152, or a separate lateral offset sensor 158 can be used to only measure the amount of lateral offset (D). For example, when only using the skew sensor 152, the initial lateral (cross-process) position of the sheet of print media 150 is detected by the skew sensor 152 as the print media 150 is initially on the rotatable transport 100. Then a processor (such as processor 224, only shown in
Methods herein thus transport the sheet of print media 150 using the marking transport 154 to a marking engine 156 and print marks on the sheet of print media 150 using the marking engine 156. After the print media 150 is delivered to the marking transport 154, the rotatable transport 100 can be re-centered, and then adjusted for the next sheet. More specifically, these methods print marks on the sheet of print media 150 using the marking engine 156 by laterally offsetting the printing marks an amount equal to the amount D the sheet of print media 150 is laterally offset from the alignment position 154B of the marking transport 154. The amount D the sheet of print media 150 is laterally offset from the alignment position 154B of the marking transport 154 (and the laterally offsetting process when printing) are in a cross-process direction that is perpendicular to the processing direction.
This processing is also shown in flowchart form in
In item 206, these methods also transport the sheet using the rotatable transport, in the compensating rotated position, to transport the sheet in the un-rotated (de-skewed) orientation to the marking transport. Note that rotational skew is only corrected by the compensating rotated position of the rotatable transport, and that the drive nips of the rotatable transport all rotate at the same rate when transporting the sheet, which avoids issues that would otherwise occur when correcting rotational skew with different nip speeds (slippage, damage, etc.).
In item 208, such methods further determine the amount the sheet is laterally offset (e.g., midline offset) in the cross-processing direction from a centerline alignment position of the marking transport. The amount of lateral offset can be determined in item 208 by making calculations from the initial sheet position measured by the skew sensor(s), or one or more separate lateral offset sensors can be used to only measure the amount of lateral offset. When only using the skew sensor in item 208, the initial lateral (cross-process) position of the sheet of print media is detected by the skew sensor as the print media is initially on the rotatable transport. Then the processing in item 208 can calculate the change in lateral position that is projected to occur based on the length of the rotatable transport and the angle of the compensating rotated position relative to the processing direction. The combination of the change in lateral position added to, or subtracted from, the initial lateral offset provides the amount the sheet of print media is laterally offset from the alignment position of the marking transport, without need of a separate lateral offset sensor.
As shown in item 210, methods herein print marks on the sheet using the marking engine. These methods print marks on the sheet using the marking engine in item 210 by laterally offsetting the printing marks an amount equal to the amount the midline of the sheet is laterally offset from the alignment position of the marking transport. The amount the sheet is laterally offset from the alignment position of the marking transport (and the laterally offsetting process) are in a cross-process direction that is perpendicular to the processing direction. Again, taking the image and “laterally” shifting the whole image over a certain number of pixels does not require as much computational bandwidth as rotational correction. Therefore, by physically correcting for sheet rotation from parallel to the processing direction by rotating the transport, and using computational bandwidth to correct for lateral shift within the marking device, the mechanical elements are simplified, without incurring a heavy computational burden on the processor.
Again, the contact elements 104 are shaped and positioned to contact items (such as sheets of print media 150) that are to be transported in a processing direction relative to the frame 100. Also, the contact elements 104 are in permanent fixed positions relative to the frame 100, and do not move relative to the frame 100. The contact elements 104 are moveable (e.g., rotatable, etc.) at such fixed positions, so as to move the items in the processing direction.
Additionally,
Note that the controller/processor 224 (discussed below) and connections thereto are only shown in
Thus, the controller 224 is electrically connected to all the adjustable mounts 106. The controller 224 is adapted to independently control the adjustable mounts 106 to simultaneously rotate the frame 100 and all the contact elements 104 in a counter-clockwise rotation (
While
More specifically, the structures shown in
Also, such alternative structures include secondary adjustable mounts 136 that are connected to the secondary frame 132 and the primary frame 100, wherein the secondary adjustable mounts 136 are connected to the secondary frame 132 in locations to move the secondary frame 132 in the processing direction relative to the primary frame 100. The secondary adjustable mounts 136 are also electrically connected to the controller 224, and the controller 224 is similarly adapted to control the secondary adjustable mounts 136 to move the secondary frame 132 parallel to the processing direction of the primary frame 100 while simultaneously rotating the primary frame 100 and moving the primary frame 100 in the cross-processing direction. This is shown, for example, in
Note that
In addition, as shown in
While belts and drive nips are mentioned above,
The input/output device 214 is used for communications to and from the printing device 254 and comprises a wired device or wireless device (of any form, whether currently known or developed in the future). The tangible processor 224 controls the various actions of the printing device 254. A non-transitory, tangible, computer storage medium device 250 (which can be optical, magnetic, capacitor based, etc., and is different from a transitory signal) is readable by the tangible processor 224 and stores instructions that the tangible processor 224 executes to allow the computerized device to perform its various functions, such as those described herein. Thus, as shown in
The printing device 254 includes at least one marking device (printing engine(s)) 240 that use marking material, and are operatively connected to a specialized image processor 224 (that is different from a general purpose computer because it is specialized for processing image data), a media path 236 positioned to supply continuous media or sheets of media from a sheet supply 230 to the marking device(s) 240, etc. After receiving various markings from the printing engine(s) 240, the sheets of media can optionally pass to a finisher 234 which can fold, staple, sort, etc., the various printed sheets. Also, the printing device 254 can include at least one accessory functional component (such as a scanner/document handler 232 (automatic document feeder (ADF)), etc.) that also operate on the power supplied from the external power source 220 (through the power supply 218).
The one or more printing engines 240 are intended to illustrate any marking device that applies marking material (toner, inks, plastics, organic material, etc.) to continuous media, sheets of media, fixed platforms, etc., in two- or three-dimensional printing processes, whether currently known or developed in the future. The printing engines 240 can include, for example, devices that use electrostatic toner printers, inkjet printheads, contact printheads, three-dimensional printers, etc. The one or more printing engines 240 can include, for example, devices that use a photoreceptor belt or an intermediate transfer belt or devices that print directly to print media (e.g., inkjet printers, ribbon-based contact printers, etc.).
While some exemplary structures are illustrated in the attached drawings, those ordinarily skilled in the art would understand that the drawings are simplified schematic illustrations and that the claims presented below encompass many more features that are not illustrated (or potentially many less) but that are commonly utilized with such devices and systems. Therefore, Applicants do not intend for the claims presented below to be limited by the attached drawings, but instead the attached drawings are merely provided to illustrate a few ways in which the claimed features can be implemented.
Many computerized devices are discussed above. Computerized devices that include chip-based central processing units (CPU's), input/output devices (including graphic user interfaces (GUI), memories, comparators, tangible processors, etc.) are well-known and readily available devices produced by manufacturers such as Dell Computers, Round Rock Tex., USA and Apple Computer Co., Cupertino Calif., USA. Such computerized devices commonly include input/output devices, power supplies, tangible processors, electronic storage memories, wiring, etc., the details of which are omitted herefrom to allow the reader to focus on the salient aspects of the systems and methods described herein. Similarly, printers, copiers, scanners and other similar peripheral equipment are available from Xerox Corporation, Norwalk, Conn., USA and the details of such devices are not discussed herein for purposes of brevity and reader focus.
The terms printer or printing device as used herein encompasses any apparatus, such as a digital copier, bookmaking machine, facsimile machine, multi-function machine, etc., which performs a print outputting function for any purpose. The details of printers, printing engines, etc., are well-known and are not described in detail herein to keep this disclosure focused on the salient features presented. The systems and methods herein can encompass systems and methods that print in color, monochrome, or handle color or monochrome image data. All foregoing systems and methods are specifically applicable to electrostatographic and/or xerographic machines and/or processes.
In addition, terms such as “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “upper”, “lower”, “under”, “below”, “underlying”, “over”, “overlying”, “parallel”, “perpendicular”, etc., used herein are understood to be relative locations as they are oriented and illustrated in the drawings (unless otherwise indicated). Terms such as “touching”, “on”, “in direct contact”, “abutting”, “directly adjacent to”, etc., mean that at least one element physically contacts another element (without other elements separating the described elements). Further, the terms automated or automatically mean that once a process is started (by a machine or a user), one or more machines perform the process without further input from any user. In the drawings herein, the same identification numeral identifies the same or similar item.
It will be appreciated that 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. Unless specifically defined in a specific claim itself, steps or components of the systems and methods herein cannot be implied or imported from any above example as limitations to any particular order, number, position, size, shape, angle, color, or material.
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