Abstract:
According to aspects described herein, there is disclosed an apparatus for de-skewing substrate media in a printing system. The apparatus includes at least one sensor for measuring skew of the substrate media being transferred relative to a process direction. The apparatus also includes a nip assembly for moving the substrate media in the process direction. The nip assembly includes a drive roller and an idler roller for engaging the substrate media. The drive roller is rotatably supported on a shaft axis, with the shaft axis being pivotally supported substantially at one end thereof for aligning the shaft axis with the measured substrate media skew. The shaft axis pivots about a pivot axis perpendicular to the shaft axis.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The following U.S. patent application is incorporated in its entirety for the teachings therein: U.S. Patent and Trademark Office application Ser. No. 12/364,675, filed Feb. 3, 2009, entitled MODULAR COLOR XEROGRAPHIC PRINTING ARCHITECTURE, assigned to the assignee hereof (Attorney File No. 20080773-US-NP). 
     
    
     TECHNICAL FIELD 
       [0002]    The presently disclosed technologies are directed to an apparatus, method and system of registering and de-skewing a substrate media in a substrate media handling assembly, such as a printing system. 
       BACKGROUND 
       [0003]    In a printing system, accurate and reliable registration of the substrate media as it is transferred in a process direction is desirable. Even a slight skew or misalignment of the substrate media through an image transfer zone can lead to image and/or color registration errors. For example, in printing systems transporting substrate media using nip assemblies or belts, slight skew of the substrate media can cause processing errors. Also, as substrate media is transferred between sections of the printing system, the amount of skew can increase or accumulate. In modular overprint systems, the accumulation of skew will translate into substrate media positioning errors between module exit and entry points, particularly in a cross-process direction. Such errors can cause large push, pull or shearing forces to be generated, which transmit to the substrate media being transported. Medium and light-weight substrate media cannot generally support large forces, which will cause wrinkling, buckling or tearing of such media. 
         [0004]    Accordingly, it would be desirable to provide an apparatus, method and system of registering and de-skewing a substrate media, which overcomes the shortcoming of the prior art. 
       SUMMARY 
       [0005]    According to aspects described herein, there is disclosed an apparatus for de-skewing substrate media in a printing system. The apparatus includes at least one sensor for measuring skew of the substrate media being transferred relative to a process direction. The apparatus also includes a nip assembly for moving the substrate media in the process direction. The nip assembly includes a drive roller and an idler roller for engaging the substrate media. The drive roller is rotatably supported on a shaft axis, with the shaft axis being pivotally supported substantially at one end thereof for aligning the shaft axis with the measured substrate media skew. The shaft axis pivots about a pivot axis perpendicular to the shaft axis. 
         [0006]    According to other aspects described herein, there is provided an apparatus for de-skewing substrate media in a printing system, wherein the nip assembly can pivot about the pivot axis. Also, the apparatus can further include an actuating member for pivoting the shaft axis about the pivot axis to an orientation parallel to an edge of the substrate media. Additionally, the actuating member can be disposed substantially at an opposed end of the shaft axis relative to the pivotal support. Further, the actuating member can include a cam assembly. Further still, the at least one sensor can include at least two sensors disposed ahead of the nip assembly in the process direction. Yet further still, the at least two sensors can be spaced apart in a cross-process direction, wherein a straight line between the two sensors is parallel to the shaft axis in a default position. The pivotal support can include a spherical bearing element. Also, both the actuating member and the sensor can be coupled to a control system for actuating the nip assembly in response to a sensor measurement. The idler roller can be biased toward the drive roller. 
         [0007]    According to further aspects described herein, there is provided a method of de-skewing substrate media in a printing system. The method includes measuring a skew angle of a substrate media transferred in a process direction. Then, pivoting an axis of rotation of a registration nip assembly to match the skew angle. The axis of rotation pivots about a support disposed laterally to a centerline of the process direction. Upon engagement of the substrate media with the registration nip assembly, then pivoting the axis of rotation to a position perpendicular to the process direction. 
         [0008]    According to yet further aspects described herein, the method can also include disengaging a further nip assembly from the substrate media prior to pivoting the axis of rotation to a position perpendicular to the process direction. Also, the further nip assembly can be disposed upstream to the registration nip assembly relative to the process direction. Additionally, the axis of rotation can be translated in a cross process direction. Further, the substrate media velocity can be measured and adjusted. Further still, the skew angle of the substrate media can be measured from an edge of the substrate media prior to engagement with the nip assembly. The pivoting of the axis of rotation can be controlled by a cam assembly. Also, the cam assembly can be actuated by a motor in response to the skew angle measurement. The registration nip assembly axis of rotation can pivot about a spherical bearing assembly. The skew angle measurement can be performed by at least one sensor disposed upstream to the nip assembly in the process direction. The spherical bearing assembly can be disposed at an opposite side of the nip assembly from a cam assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a partially schematic side view of a substrate media registration and de-skew apparatus for use with a printing system. 
           [0010]      FIG. 2  is a partially schematic plan view of a substrate media registration and de-skew apparatus for use with a printing system. 
           [0011]      FIG. 3  is a partially schematic plan view of the apparatus of  FIG. 2 , with a nip assembly skewed to substantially conform to a handled substrate media. 
           [0012]      FIG. 4  is a partially schematic plan view of the apparatus of  FIG. 3 , with the nip assembly and substrate media adjusted to a default position. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Describing now in further detail these exemplary embodiments with reference to the Figures, as described above the substrate media registration and de-skew apparatus and method are typically used in a select location or locations of the paper path or paths of various conventional printing assemblies. Thus, only a portion of an exemplary printing system path is illustrated herein. 
         [0014]    As used herein, a “printer” or “printing system” refers to one or more devices used to generate “printouts” or a print outputting function, which refers to the reproduction of information on “substrate media” for any purpose. A “printer” or “printing system” 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. 
         [0015]    A printing system can use an “electrostatographic process” to generate printouts, which refers to forming and using electrostatic charged patterns to record and reproduce information, a “xerographic process”, which refers to the use of a resinous powder on an electrically charged plate record and reproduce information, or other suitable processes for generating printouts, such as an ink jet process, a liquid ink process, a solid ink process, and the like. Also, such a printing system can print and/or handle either monochrome or color image data. 
         [0016]    As used herein, “substrate media” refers to, for example, paper, transparencies, parchment, film, fabric, plastic, or other substrates on which information can be reproduced, preferably in the form of a sheet or web. 
         [0017]    As used herein, “sensor” refers to a device that responds to a physical stimulus and transmits a resulting impulse for the measurement and/or operation of controls. Such sensors include those that use pressure, light, motion, heat, sound and magnetism. Also, each of such sensors as refers to herein can include one or more point sensors and/or array sensors for detecting and/or measuring characteristics of a substrate media, such as speed, orientation, process or cross-process position and even the size of the substrate media. Thus, reference herein to a “sensor” can include more than one sensor. 
         [0018]    As used herein, “skew” refers to a physical orientation of a substrate media relative to a process direction. In particular, skew refers to a misalignment, slant or oblique orientation of an edge of the substrate media relative to a process direction. 
         [0019]    As used herein, the terms “process” and “process direction” refer to a process of printing or reproducing information on substrate media. The process direction is a flow path the substrate media moves in during the process. A “cross-process direction” is lateral to the process direction. 
         [0020]      FIG. 1  depicts a partially schematic side view of a substrate media registration and de-skew apparatus for use with a substrate media handling system, preferably for a printing system. It should be noted that the partially schematic drawings herein are not to scale. In  FIG. 1 , arrow  10  represents the direction of flow of the substrate media, which corresponds to the process direction, from an upstream location toward a downstream location. In this way, the substrate media travels across a registration and de-skew area where a nip assembly  110  is located. Two baffles  25  are preferably provided above and below the substrate media path  10 . Preferably, the baffles are equidistantly spaced away from a substrate media centerline  35  and act as guides for the substrate media as it approaches and moves beyond the nip assembly  110  in the flow direction  10 . 
         [0021]    Preferably, each nip  115  includes a drive roll  120  and an idler  130 . The drive roll  120  and idler  130  of the nip tend to touch one another along a contact line. Thus, the nip  115  is used to engage and grab substrate media and moves it through the overall assembly. While not shown, a spring is preferably center loaded against the idler shaft  132  biasing the driver roll  120  and idler  130  toward one another, thus supplying a gripping force for the nips  115 . The default position for the drive shaft  122  and the idler shaft  132  is in a plane  20 , which is preferably perpendicular to the flow path  10 . Also, preferably the drive shaft  122  and the idler shaft  132  are supported in a parallel configuration in that common registration plane  20  when in the default position. The registration plane  20  vertically traverses the substrate media flow path  10 . Preferably, the drive rolls  120  from each nip  115  are supported by a common drive shaft  122 . Similarly, the idlers  130  from each nip  115  are supported by a common idler shaft  132 . Thus, at least the drive rolls  120 , drive shaft  122 , idlers  130  and idler shaft  132  are considered part of an overall nip assembly  110 . As shown in  FIGS. 2-4 , more than one nip  115  is preferably supported by the drive shaft  122  and the idler shaft  132 . Also, a cam follower  124  is preferably supported by the drive shaft  122 . The cam follower  124  is adapted to be engaged with a cam  160 . The cam  160  is used as an actuating member to alter the orientation or angle of the nip assembly  110  in the direction of flow  10 . Preferably, the drive shaft  122  is biased toward the cam  160 . 
         [0022]      FIG. 2  is a partially schematic plan view of the apparatus shown in  FIG. 1 . The two nips  115  are spaced apart laterally across the flow path  10 . For illustrative purposes, the drive shaft  122  alone is shown in the plan view drawings herein, as it is understood that the drive shaft  122  and idler shaft  132  preferably remain parallel. The drive shaft  122  is supported by bearings  140 ,  150  that allow the drive shaft  122  to rotate freely along its axis. The cam  160  can shift the position of the inboard bearing  150 . The cam  160  is supported by a cam shaft  170  that is driven by a motor, which is preferably a stepper motor (not shown). The outboard bearing  140  preferably differs from inboard bearing  150  in that the outboard bearing  140  includes a spherical bearing element  145  that in addition to axial rotation, provides for pivotal movement A of the drive shaft  122 . In this way, as the cam  160  is rotated, the inboard side of the nip assembly  110  will move in an arch A in either the upstream or downstream direction, depending on how the cam  160  is rotated. When the inboard side pivots, the outboard side of the nip assembly  110  pivots about spherical bearing element  145 . Thus, the nip assembly pivots about a pivot axis centered on the spherical bearing element  145 , which pivot axis is perpendicular to both the process direction and the cross-process direction. The idler shaft  132  is supported in such a way that it will follow and remain parallel to the drive shaft  122  as it pivots. For example, in inboard side of the nip assembly  110  can be supported in an oval guide yoke (not shown), that allows the inboard bearing to float. The pivotal movement A of the nip assembly  110  is preferably controlled by turning the cam  160  a specific amount using the attached motor. 
         [0023]    Upstream of the nip assembly  110  are sensors S 1 , S 2 , S 3 . The sensors S 1 , S 2 , S 3  preferably detect the orientation of the substrate media as it approaches the registration and de-skew area. While two (2) to three (3) sensors are shown in  FIGS. 2-4 , it should be understood that fewer or greater numbers of sensors could be used, depending on the type of sensor, the desired accuracy of measurement and redundancy needed or preferred. For example, a pressure or optical sensor could be used to detect when the substrate media passes over each individual sensor. Additionally, the sensors can be positioned further upstream or closer to the registration and de-skew area as necessary. It should be appreciated that any sheet sensing system can be used to detect the position and/or other characteristics of the substrate media in accordance with the disclosed technologies. 
         [0024]    In one embodiment shown in  FIGS. 3 and 4 , at least two sensors S 1 , S 2  are provided that are spaced apart from one another in a parallel configuration relative to the drive shaft  122  default position, shown in  FIG. 1 . Preferably, these sensors S 1 , S 2  are also parallel to other upstream/downstream processes, such as the photoreceptor(s) and the image transfer zone. Such parallel alignment of these sensors S 1 , S 2  is preferably “zeroed out” during the set up of the overall assembly. Alternatively an automated mechanism can be provided for maintaining parallel alignment. The sensors S 1 , S 2  will individually detect when they are blocked by the substrate media  5 . By registering the difference in the time that sensors S 1 , S 2  are blocked by the substrate media  5  and knowing the velocity, the skew of the substrate media  5  relative to registration plane  20  and relative to a downstream transfer zone. As shown in  FIG. 1 , where a third sensor S 3  is positioned adjacent to S 1  and a known dimension downstream, the velocity of the substrate media  5  can be more accurately measure. 
         [0025]      FIG. 3  shows a skewed substrate media  5  approaching the registration and de-skew area. As the substrate media  5  crosses the sensors S 1 , S 2 , the skew is measured and registered by automated control systems. Then, prior to the substrate media  5  arriving at the registration plane  20 , the nip assembly  110 , including the drive shaft  122  and idler shaft  132 , is pivoted to match the measured skew. As shown in  FIG. 3 , the control system pivots the nip assembly  110  in direction B 1  by actuating the motor that controls the cam  160 . During this pivotal movement, the drive shaft  122  and idler shaft  132  remain parallel to one another in a plane  22 , which represents a nip assembly central plane. Once the nip assembly  110  is skewed to match the substrate media  5 , the nip plane  22  will form an angel θ with the registration plane  20 . Once the nip assembly  110  engages the substrate media  5 , any additional upstream or downstream nips (not shown) are preferably opened. In this way, those additional nips release the substrate media  5  so it can be freely adjusted. The cam  160  can then be driven by the motor in direction B 2  back to its default position.  FIG. 4  shows the nip assembly  110  in the default position. This pivotal rotation to the default position pulls or shifts the substrate media  5  substantially into alignment with the downstream transfer zone. 
         [0026]    Alternatively, if the sensors S 1 , S 2  detect that the incoming substrate media  5  is substantially aligned with the default position (no significant skew), then no de-skewing is preferably performed. The substrate media  5  can then proceed through the nip assembly and encouraged toward the downstream transfer zone without pivoting the drive shaft  122 . 
         [0027]    Additionally, regardless of whether the pivotal de-skewing is performed as described above, further cross-process positioning can occur once the substrate media  5  is engaged by the nip assembly  110 . Also, process positioning and timing can also be adjusted in the registration and de-skew area. During any additional adjustment of the cross-process or process positioning or timing, the previous downstream nips are preferably opened to allow the substrate media  5  to be adjusted more freely. Functions such as cross-process positioning can be achieved by shifting sideways (lateral to the process direction  10 ) a substantial portion of the drive mechanism. Further sensors, such as edge sensor can be used to detect when the substrate media  5  is properly positioned. Any process positioning or timing can be accomplished though careful control of the drive shaft velocity. 
         [0028]    Often printing systems include more than one printing module or station. Accordingly, more than one nip assembly  110  can be included in an overall printing system. Further, it should be understood that in a modular system or a system that includes more than one nip assembly  110 , in accordance with the disclosed technologies herein, could detect substrate media position and relay that information to a central processor for controlling registration and/or skew in the overall printing system. Thus, if the registration and/or skew is too large for one nip assembly  110  to correct, then correction can be achieved with the use of more than one nip assembly  110 , for example in another module or station. 
         [0029]    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.