Patent Publication Number: US-8109499-B2

Title: Methods for moving a media sheet within an imaging device

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is related to application Ser. No. 12/750,318 entitled “Methods for Moving a Media Sheet within an Imaging Device” assigned to the same assignee as the present application. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     REFERENCE TO SEQUENTIAL LISTING, ETC. 
     None. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates generally to a printing peripheral, and more specifically to a method for moving a media sheet within an imaging device and entering the media sheet into a feed nip in a substantially deskewed alignment. 
     2. Description of the Related Art 
     Conventional printers, scanners, and all-in-one devices utilize a series of rollers to pick a media sheet and move the media sheet along a media path within the device. The media sheet is moved to a feedroll that advances the media sheet into the scanning or image transfer section of the device. A primary cause of paper jams is an incomplete pick resulting from the media sheet not reaching the feedroll. The optimal rotational distance required to move a media sheet from a known point to the feedroll can be difficult to determine due to slipping from mechanical and frictional variations and differing media stiffness. 
     In order to avoid a paper jam, the device&#39;s rollers must push the media sheet the entire distance to the feed roller. If the rollers are stopped too soon, the media sheet will not make it to the feed rollers and a paper jam may result. However, if the rollers run too long unpleasant noise and unnecessary tire and motor wear may occur. Further, if the rollers run too long, in some instances, the media sheet may be pressed against the feed rollers too hard thereby resulting in folds or dents in the paper. Previously, the method to address this situation was to set the distance from a known point, such as the location of a sensor, to the feed rollers for each media type to the longest needed throughout the printer life. This method reduces the probability of a paper jam. However, as previously stated, this may result in unpleasant noise and unnecessary wear. This method also requires the user to select the correct media type and/or the media detection of the device to properly detect the media type. 
     It is also desirable that the media sheet enter the feed rollers in a substantially deskewed alignment. If the media sheet is skewed as it enters the feedroll, the media sheet will be skewed when it passes through the scanning section or the image transfer section. Consequently, the resulting scan or print will also be skewed. 
     Given the foregoing, it will be appreciated that a method for moving a media sheet within an imaging device that adaptively determines the optimum rotational distance to the feedroll for various media types is preferable. It is also preferable to adjust to variation between devices and to changes over the life of a device. Further, it is preferable that such method provide for entry of the media sheet into the feedroll in a substantially deskewed alignment. 
     SUMMARY OF THE INVENTION 
     According to an exemplary embodiment, a first method for moving a media sheet within an imaging device includes moving the media sheet along a media path by rotating a roller. While the media sheet is moving, a first sensor is activated with the leading edge of the media sheet and then a second sensor is activated with the leading edge of the media sheet. The number of rotations of the roller during a time period T S1,S2  between activation of the first sensor and activation of the second sensor by the leading edge of the moving media sheet is determined. A measured distance D M  from the first sensor to the second sensor based on the number of rotations of the roller during the time period T S1,S2  is calculated. An adjusted distance D A  from the second sensor to a feed nip is then calculated by multiplying the measured distance D M  from the first sensor to the second sensor by a constant based on at least one predetermined distance in the media path. Further, embodiments include those wherein the constant is equal to a predetermined reference distance from the second sensor to the feed nip divided by a predetermined reference distance from the first sensor to the second sensor. The constant is stored in a memory within the imaging device and corresponds with a pick mode selected from the group consisting of direct pick, indirect pick, and duplex pick. After activation of the second sensor, the media sheet continues to move along the media path via the roller and the roller is rotated at least the adjusted distance D A . The media sheet then enters into the feed nip in a substantially deskewed alignment and the roller is stopped. After the media sheet is entered into the feed nip, the media sheet is moved into a print zone for printing or into a scan zone for scanning. 
     Further, according to an exemplary embodiment, a second method for moving a media sheet within an imaging device includes moving a media sheet along a media path by rotating a roller driven by a motor. The leading edge of the media sheet activates a sensor downstream from the roller. After activating the sensor with the media sheet, the roller is rotated at least a predetermined distance D. After rotating the roller at least a distance D P , the leading edge of the media sheet is past an entrance to a duplex path along the media path. A processor then begins monitoring whether a performance attribute of a component of the imaging device has satisfied a predetermined criteria. The distance D P  corresponds with a specific pick mode and is stored in a memory within the imaging device. After the performance attribute of the component of the imaging device satisfies the predetermined criteria, the media sheet is entered into a feed nip in a substantially deskewed alignment and the roller is stopped. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of the various embodiments of the invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of an exemplary imaging device; 
         FIG. 2  is a side view of the media path according to an embodiment of the present invention; 
         FIGS. 3-7  are sequence views of a media sheet moving on the media path in the imaging device; 
         FIG. 3  is a side view of the media path showing the media sheet advanced on a simplex path; 
         FIG. 4  is a side view of the media path showing the media sheet advanced on the simplex path through a feed nip into a print zone; 
         FIG. 5  is a side view of the media path showing the media sheet advanced into a duplex path; 
         FIG. 6  is a side view of the media path showing the media sheet advanced from the duplex path back into the simplex path; 
         FIG. 7  is a side view of the media path showing the media sheet advanced back into the print zone for duplex printing; 
         FIG. 8  is a flow chart of a method for moving a media sheet through an imaging device; and 
         FIG. 9  is a flow chart of a method for moving a media sheet through an imaging device. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. 
     In addition, it should be understood that embodiments of the invention include both hardware and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. 
     With reference to  FIG. 1 , an imaging device  10  is shown having a scanner portion  12  and a printer portion  20  included therewith. The imaging device  10  further comprises a housing  22  wherein the mechanical parts are contained for scanning and printing. The housing  22  is generally box-like in shape but various geometries may be utilized. Within the housing  22  is the printer portion  20  that may be defined by a laser printer, a thermal inkjet printer, a piezo-electric inkjet printer, dye sublimation or other image forming technology. The exemplary embodiment includes an input tray  24  for receiving and supporting a plurality of blank media sheets and an output tray  26  for receiving and supporting the media sheets after the printing process. The imaging device  10  may also comprise a control panel  11  including a plurality of buttons and a display, such as a liquid crystal display (LCD), providing various notifications, menus, and selection options. 
     The scanner portion  12  generally includes a flat bed scanner, generally indicated beneath a flat-bed scanner lid  15  and an auto-document feed (ADF) scanner  14 . The ADF scanner  14  comprises an input tray  16  and output tray  18 . The input tray  16  receives and supports one or more stacked documents for feeding one sheet at a time through the ADF scanner  14 . The output tray  18  receives and supports the documents following the scanning process and is generally formed on the upper surface of the scanner lid  15 . The flat-bed scanner comprises a transparent platen beneath the lid  15  for manual positioning of target media for scanning. The scanner portion  12  is generally disposed on an upper portion of the imaging device  10  above the printer portion  20  although alternate configurations may be utilized. The scanner lid  15  is hingedly attached along the rear edge of the housing  22 . The scanner lid  15  may be moved with respect to a scanner bed between a closed position shown in  FIG. 1  and an open position (not shown) revealing the transparent platen. 
     With reference to  FIG. 2 , the imaging device  10  includes a media path  32  which includes a simplex path  34 . The imaging device  10  illustrated includes a C-shaped simplex path  34 . However, one skilled in the art will understand that the present invention may utilize alternative simplex feed path designs, such as an L-shaped simplex path and that such designs are well within the scope of the present invention. The C-shaped simplex path  34  is shown merely for ease of description. Embodiments include those wherein the media path  32  further comprises a duplex path  50 . The media sheets are stored in the input tray  24  in a media stack M. A pick mechanism  35  initiates movement of a media sheet from the media stack M into the simplex path  34 . The pick mechanism  35  may comprise an auto-compensating mechanism (ACM) as shown in  FIG. 2 . The pick mechanism  35  includes a pick roller  35   a  in physical contact with the top most sheet of the media stack. The pick roller  35   a  is driven by a motor (not shown). The rotation of the pick roller  35   a  causes the media to advance upward, one sheet at a time, into the simplex path  34 . In some embodiments, the pick roller  35   a  includes sensing means for determining the angular displacement of the pick roller  35   a  such as, for example, an encoder wheel. Embodiments include those wherein sensing means are used to determine the number of rotations of the pick roller  35   a . Data related to the angular displacement of the pick roller  35   a  is transmitted to a processor (not shown). 
     Downstream from the pick roller  35   a , along the simplex path  34 , is a roller  36 . The roller  36  may comprise an auto-compensating mechanism (ACM)  36   a  as illustrated. The roller  36  is driven by a motor (not shown). The roller  36  may also have a corresponding pressure roller  36   b  such that the motor-driven roller  36  and the pressure roller  36   b  form a nip  36   c . The ACM  36   a  may be pivotable so as to move the roller  36  and, in turn, open and close the nip  36   c . Alternatively, the ACM  36   a  may be fixed so that the roller  36  is in an engaged position with the pressure roller  36   b . The nip  36   c  receives the leading edge of a media sheet moving through the simplex path  34 . The roller  36  rotates thereby causing the media sheet to advance through the media path  32  toward a first sensor  80 . In some embodiments, the roller  36  includes sensing means for determining the angular displacement of the roller  36  such as, for example, an encoder wheel. Embodiments include those wherein sensing means are used to determine the number of rotations of the roller  36 . Data related to the angular displacement of the roller  36  is transmitted to the processor. 
     As the media sheet passes the first sensor  80 , the first sensor  80  is activated. The first sensor  80  then signals the media location to the processor. In some embodiments, the first sensor  80  is activated by the leading edge of the media sheet. The media sheet continues to travel along the media path  32  toward a second sensor  84 . As the media sheet passes the second sensor  84 , the second sensor  84  is activated. The second sensor  84  then signals the media location to the processor. In some embodiments, the second sensor  84  is activated by the leading edge of the media sheet. In the exemplary embodiment illustrated, the first sensor  80  and the second sensor  84  comprise a mechanical flag sensor. Alternatively, the first sensor  80  and the second sensor  84  may include an optical sensor or any other suitable means for sensing the presence of a media sheet. 
     Downstream from the first sensor  80  is a gate  86  located generally at a first intersection  90  between the simplex path  34  and the duplex path  50 . In the exemplary embodiment illustrated, the gate  86  is upstream from the second sensor  84 . Alternatives include those wherein the second sensor  84  is upstream from the gate  86 . The gate  86  inhibits the trailing edge of a media sheet from being reversed into the simplex path  34 . Alternatively stated, the gate  86  directs media sheets moving from the feed nip  37  toward the duplex path  50 . 
     Downstream from the second sensor  84  is a feed nip  37 . In the exemplary embodiment illustrated, the feed nip  37  is formed by a pair of feed rollers  37   a  and  37   b . The feed rollers  37   a  and  37   b  advance the media sheet through a print zone  60 . Alternatives include those wherein the feed nip  37  is formed by a feed roller and a surface. The exemplary feed nip  37  illustrated comprises a reversible feed roll  37   a  and an opposite pressure roll  37   b  wherein the feed rollers  37   a  and  37   b  are capable of moving a media sheet from the simplex path  34  toward the print zone  60  and moving the media sheet away from the print zone  60  into the duplex path  50 . 
     Downstream from the feed nip  37  is the print zone  60 . In the embodiment illustrated, the print zone  60  includes a print cartridge  29 . The print cartridge  29  selectably ejects ink onto one or both surfaces of the media sheet during simplex or duplex printing, respectively. Alternatives include those wherein an image is transferred to the media sheet by a photoconductive drum as used by a laser printer, by dye sublimation or by any other suitable image forming technology. 
     Downstream from the print zone  60  along the simplex path  34  is an exit drive system  38  comprising at least one roller. The exemplary embodiment shown includes two driven rollers  38   a  and  38   b  and two pressure rollers  38   c  and  38   d . The exit drive system  38  receives the media sheet from the feed nip  37  and directs the media sheet to the output tray  26 . The output tray  26  resides downstream along the simplex path  34  and receives finished printed media sheets. 
     In the exemplary embodiment illustrated, adjacent the simplex path  34  is the duplex path  50 . Extending from the feed nip  37  toward the duplex path  50  is the first section of the duplex path  50   a . The first section of the duplex path  50   a  extends from a first intersection  90  between the simplex path  34  and the duplex path  50 . The duplex path  50  further comprises a second section  50   b  which is substantially C-shaped. Extending from the second section  50   b  is a third section  50   c  of the duplex path  50 . The third section  50   c  feeds back into the simplex path  34  at a second intersection  92  between the simplex path  34  and the duplex path  50 . 
     The exemplary embodiment illustrated in the figures includes one roller  36  disposed on the simplex path  34  between the pick roller  35   a  and the feed nip  37 . Alternatives include those wherein additional rollers are disposed on the simplex path  34  such as, for example, two rollers spaced apart on the media path  32  wherein the first roller  36  is upstream from the first sensor  80  and the second roller (not shown) is between the first sensor  80  and the second sensor  84 . 
       FIGS. 3-7  illustrate a sequence of side-views wherein a media sheet S moves through the imaging device  10  during a duplex feeding process. Referring first to  FIG. 3 , a side view of an exemplary embodiment is depicted. Specifically, the figure depicts a stack of media M within the input tray  24  engaged by the pick roller  35   a . The pick roller  35   a  has engaged the top most media sheet S of the media stack M and advanced the media sheet S along the simplex path  34 . The media sheet S has advanced to the roller  36 . The rotation of roller  36  further advances the media sheet S along the simplex path  34 . The leading edge of the media sheet S has activated the first sensor  80 . 
     With reference to  FIG. 4 , the roller  36  continues to move the media sheet S along the simplex path  34 . The media sheet S has passed through the gate  86 , activated the second sensor  84  and advanced through the feed nip  37  and into the print zone  60 . In one embodiment, before the trailing edge of the media sheet S passes through the feed nip  37 , in order to accomplish a duplex print, the direction of movement of the media sheet S is reversed. In another embodiment, allowing for printing to the trailing edge of the media sheet S, the direction of movement of the media sheet S is reversed at the exit roller  38 . 
       FIGS. 3 and 4  illustrate an indirect pick where the media sheet S is first moved by the pick roller  35   a  and then by the roller  36  until it reaches the feed nip  37 . In some embodiments, the imaging device  10  comprises additional intermediate rollers disposed on the media path  32  between the pick roller  35   a  and the feed nip  37 . In these embodiments, an indirect pick is accomplished using a combination of the pick roller  35   a , the roller  36  and the intermediate rollers. Alternatives include those wherein a direct pick is used where the media sheet S is advanced from the media stack M to the feed nip  37  by the pick roller  35   a.    
     With reference to  FIG. 5 , the media sheet S is advanced through the duplex path  50  by the feed roller  37   a . The gate  86  ensures that the media sheet S enters the duplex path  50  and not the simplex path  34 . The media sheet S travels around the duplex path  50  and into the nip  36   c  formed by the roller  36  and the corresponding roller  36   b . In the exemplary embodiment illustrated, the duplex path  50  does not utilize rollers specific to the duplex path  50 . Rather, the duplex path  50  merely guides the media sheet S as it is driven by the feed nip  37  and the roller  36 . Alternatives include those wherein the duplex path  50  includes a roller disposed on the duplex path  50  for advancing the media sheet S through the duplex path  50 . 
     With reference to  FIG. 6 , the media sheet S is released from the feed nip  37  and driven by the roller  36  back towards the print zone  60 . The media sheet S passes from the duplex path  50  to the simplex path  34  at the second intersection  92 . With reference to  FIG. 7 , the media sheet S is driven by the roller  36  through the feed nip  37 . The feed roller  37   a  then advances the media sheet S into the print zone  60 . After printing, the media sheet S is ready to discharge to the output tray  26 , thereby completing a duplex printing cycle. One skilled in the art will understand that as the media sheet S is advanced through the duplex path  50 , the media changes orientation relative to the print cartridge  29 . Specifically, as the media sheet S first passes the print cartridge  29  via the simplex path  34 , the first (obverse) side of the media sheet S is exposed to the print cartridge  29 . As the media sheet S reverses direction and passes through the duplex path  50 , the media sheet S returns to the print cartridge  29  with the second (reverse) side of the media sheet S exposed to the print cartridge  29  for the duplex printing process. 
       FIGS. 5-7  demonstrate a duplex pick where the media sheet S is advanced through the duplex path  50  by the feed roller  37   a  or the exit drive system  38  until it reaches the simplex path  34  at which point the media sheet S is advanced to the feed nip  37  by the roller  36 . In some embodiments, additional intermediate rollers are used including rollers on the duplex path  50  or rollers on the simplex path  34  either upstream or downstream from the roller  36 . 
     Referring to  FIG. 8 , a first method for moving a media sheet within an imaging device is provided. At  101 , a media sheet S is moved along the media path  32  by at least one roller R such as, for example, the roller  36 , the pick roller  35   a , and/or an intermediate roller (not shown) which may be located between the roller  36  and the feed nip  37 . As the at least one roller R rotates, feedback is received by the processor from an encoder wheel or other sensing means for tracking the number of rotations of the at least one roller R. At  102 , the first sensor  80  is activated by the moving media sheet S at time T S1 . The location of the media sheet at time T S1  is signaled to the processor. At  103 , the second sensor  84  is activated by the moving media sheet S at time T S2 . The location of the media sheet at time T S2  is signaled to the processor. 
     At  104 , the processor calculates a distance D M  where D M  is a measured distance from the first sensor  80  to the second sensor  84  based on the feedback received indicating the number of rotations of the at least one roller R during a time period T S1,S2  between activation of the first sensor  80  by the moving media sheet S at time T S1  and activation of the second sensor  84  by the moving media sheet S at time T S2 . Each roller within the imaging device  10  includes a predetermined rotation distance D REF  corresponding with a predetermined number of rotations of the roller such as, for example, a single rotation. For example, where D REF  is based on a single rotation, the predetermined rotation distance D REF  for a given roller is equal to the circumference of a portion of the roller in contact with the media sheet. The predetermined rotation distance D REF  for each roller is stored in a memory within the imaging device  10 . The processor calculates the distance D M  between the location of the first sensor  80  and the location of the second sensor  84  by multiplying the number of rotations of the at least one roller R driving the media sheet S during the time period T S1,S2  by the predetermined rotation distance D REF  of the at least one roller R. Accordingly, the measured distance D M  is a function of the rotational distance traveled by the at least one roller R during the time period T S1,S2 . Therefore, the measured distance D M  does not necessarily equate with the physical distance between the first sensor  80  and the second sensor  84 . Generally, the measured distance D M  will be greater than the physical distance between the first sensor  80  and the second sensor  84  because the at least one roller R experiences slip in relation to the media sheet S and other motion loss. Accordingly, the measured distance D M  accounts for this slip and motion loss. Where a plurality of rollers are used to move the media sheet S between the first sensor  80  and the second sensor  84 , the rotation distance of each roller must be added together in order to determine the total measured distance D M . For example if a first roller advances the media sheet S one-third of the way from the first sensor  80  to the second sensor  84  and a second roller advances the media sheet S the remaining distance to the second sensor  84 , the rotational distance of the first roller and the second roller must be added together in order to determine the total measured distance D M . 
     At  105 , the processor calculates D A  where D A  is an adjusted distance from the second sensor  84  to the feed nip  37 . The adjusted distance D A  is equal to the measured distance D M  from the first sensor  80  to the second sensor  84  multiplied by a constant X which is based on at least one predetermined distance in the media path  32 . The constant X is stored in the memory within the imaging device  10 . In some embodiments, the constant X is equal to C divided by B where B is a predetermined reference distance from the first sensor  80  to the second sensor  84  and C is a predetermined reference distance from the second sensor  84  to the feed nip  37 . In some embodiments, the predetermined reference distances B and C are stored in the memory of the imaging device  10 . In order to account for variances in slip and motion loss associated with different pick modes, the constant X and the predetermined reference distances B and C may correspond with a pick mode such that a direct pick will have constants X 1 , B 1 , C 1 , an indirect pick will have constants X 2 , B 2 , C 2 , and a duplex pick will have constants X 3 , B 3 , C 3 . The reference distances B and C may correspond with the physical distances from the first sensor  80  to the second sensor  84  and from the second sensor  84  to the feed nip  37 , respectively, such that if the distance from the first sensor  80  to the second sensor  84  is twice the distance from the second sensor  84  to the feed nip  37  then B will be twice C. However, this relationship may be altered in order to account for variation in the slip and/or motion loss experienced between the second sensor  84  and the feed nip  37  in comparison with the slip and/or motion loss experienced between the first sensor  80  and the second sensor  84 . As a result of the calculation performed at  105 , D A  factors in the unexpected slip or motion loss experienced between the first sensor  80  and the second sensor  84  and anticipates that such slip or motion loss will also occur between the second sensor  84  and the feed nip  37 . Further, the adjusted distance D A  factors in media differences, variation between devices, and changes over the life of the device. 
     At  106 , after activation of the second sensor  84 , the at least one roller R is rotated at least a distance D A . By rotating the at least one roller R at least the distance D A , slip and motion loss are accounted for thereby ensuring that the media sheet S is advanced all the way to the feed nip  37 . When the media sheet S arrives at the feed nip  37 , the feed rollers  37   a  and  37   b  are stopped or rotating toward the entrance to the duplex path  50  thereby preventing the media sheet S from entering the feed nip  37 . Rotating the at least one roller R at least the distance D A  ensures that the media sheet S is advanced until the leading edge of the media sheet S is flush with the entrance to the feed nip  37  thereby ensuring that the media sheet S will enter the feed nip  37  in a substantially deskewed alignment. After the leading edge of the media sheet S is flush with the entrance to the feed nip  37 , the feed rollers  37   a  and  37   b  begin to rotate in the direction of movement along the simplex path  34 , advancing the media sheet S through the feed nip  37 . Rotating the at least one roller R at least the distance D A  also ensures that the amount of slip and motion loss is not overestimated. If the slip or motion loss is overestimated the at least one roller R will rotate for an excessive amount of time which may cause wear to the at least one roller R and, in some instances, unpleasant noise. Embodiments include those wherein after the at least one roller R is rotated at least a distance D A , the at least one roller R is stopped. Rotation of the at least one roller R is no longer necessary to advance the media sheet S because once the media sheet S enters the feed nip  37 , the feed roller  37   a  will advance the media sheet S. At  107 , the media sheet S is entered into the feed nip  37  in a substantially deskewed alignment. 
     One skilled in the art will understand that the foregoing method is suitable for use in embodiments and alternatives other than those illustrated in the figures such as instances where it is desirable to advance a media sheet along a media path to a feed nip and to enter the media sheet into the feed nip in a substantially deskewed alignment. For example, the foregoing method may be applied to an ADF scanner  14  in order to ensure that a media sheet traveling through the automatic document feed enters feed rollers in a substantially deskewed alignment. 
     Depending on the length of the media sheet S, when moving on the duplex path  50 , the trailing edge of the media sheet S may pass the second sensor  84  before the leading edge of the media sheet S arrives at the second sensor  84  along the simplex path  34 . However, where the media sheet S is of a longer length, the trailing edge of the media sheet S may not pass the second sensor  84  before the leading edge of the media sheet S arrives at the second sensor  84  along the simplex path  34 . Accordingly, a method for moving a media sheet within an imaging device utilizing one sensor is desirable. 
     With reference to  FIG. 9 , a second method for moving a media sheet within an imaging device is provided. At  201 , a media sheet S is moved along the media path  32  by a roller R such as, for example, the roller  36 , the pick roller  35   a , and/or an intermediate roller (not shown) which may be located between the roller  36  and the feed nip  37 . In some embodiments, the roller R rotates at a substantially constant velocity when advancing the media sheet S. 
     At  202 , the media sheet S is moved past a predetermined point P P  along the media path. The point P P  is disposed sufficiently downstream on the simplex path  34  from the roller R to reasonably ensure that the satisfaction of the predetermined criteria measured in step  203  is a result of the media sheet S arriving at the entrance to the feed nip  37  and not due to minor bumps or irregularities along the media path  32  or other factors. In those embodiments where the media path  32  includes both a simplex path  34  and a duplex path  50 , the point P P  is downstream, in terms of the direction of media sheet movement on the simplex path  34 , from both intersection points  90  and  92  of the simplex path  34  and the duplex path  50 . This ensures that the predetermined criteria measured in step  203  is a result of the media sheet S arriving at the entrance to the feed nip  37  and not to the leading edge of the media sheet S contacting a trailing portion of the media sheet S entering the duplex path  50 . The point P P  may be stored in a memory in the imaging device  10 . 
     In some embodiments, the media sheet S activates a sensor, such as, for example, the first sensor  80  or the second sensor  84 , adjacent to the media path  32 . The predetermined point P P  can then be determined using the sensor as a starting point for measuring the distance to point Pp. After the media sheet S activates the sensor, the roller R is rotated a predetermined distance D. The distance D P  is stored in a memory in the imaging device  10 . In some embodiments, the distance D p  corresponds with a pick mode such that a direct pick will have a predetermined distance D P1 , an indirect pick will have a predetermined distance D P2 , and a duplex pick will have a predetermined distance D P3 . Similarly, the distance D P  may correspond with a media type such as, for example, cardstock, photo paper, or multipurpose paper. The point P P  is determined by the position of the leading edge of the media sheet on the media path after rotating the roller the distance D. Accordingly, the location of the point P P  may differ for each media sheet depending on the slip and/or motion loss experienced. Further, the point P P  may correspond with a pick mode or a media type. Rotating the roller R the distance D P  ensures that the predetermined criteria measured in step  203  is a result of the media sheet S arriving at the entrance to the feed nip  37  and not to the leading edge of the media sheet S contacting a trailing portion of the media sheet S entering the duplex path  50 . 
     At  203 , the processor monitors whether a performance attribute of a component of the imaging device  10  satisfies a predetermined criteria. In some embodiments, the performance attribute of the component of the imaging device  10  comprises an input voltage of the motor driving the roller R. In these embodiments, in order to satisfy the predetermined criteria, the input voltage of the motor must exceed a predetermined voltage value for a predetermined amount of time. The predetermined voltage value is large enough to indicate that the media sheet S has encountered the resistance along the media path  32  associated with the media sheet&#39;s arrival at the entrance to the feed nip  37 . However, the predetermined voltage value is lower than the voltage value typically associated with a motor stall. This ensures that the motor does not stall as a result of the media sheet&#39;s contact with the feed nip  37 . The predetermined amount of time must be long enough to confirm that the increase in input voltage is due to the arrival of the media sheet S at the entrance to the feed nip  37  and not to minor bumps or irregularities along the media path  32 . The predetermined amount of time is typically shorter than a time period that would be used to detect a motor stall. This is desirable to ensure that the motor does not stall. The predetermined amount of time in one exemplary embodiment is about 10 ms. 
     Alternatives include those wherein the performance attribute of the component of the imaging device  10  comprises the velocity of the roller R. In these alternatives, in order to satisfy the predetermined criteria, the velocity of the roller R must fall below a predetermined velocity value for a predetermined amount of time. The predetermined velocity value is low enough to indicate that the media sheet S has encountered the resistance along the media path  32  associated with the media sheet&#39;s S arrival at the entrance to the feed nip  37 . 
     In some alternatives, these criteria are combined such that the performance attribute of the component of the imaging device  10  comprises the velocity of the roller R and the input voltage of the motor. In order to satisfy the predetermined criteria, the velocity of the roller R must fall below the predetermined velocity value for a first predetermined amount of time and the input voltage must exceed the predetermined voltage value for a second predetermined amount of time. The first predetermined amount of time may be equal to the second predetermined amount of time. Further, in some embodiments, the first predetermined amount of time is concurrent with the second predetermined amount of time. 
     Alternatively, the performance attribute of the component of the imaging device  10  may comprise a torque of the motor driving the roller R. In these alternatives, in order to satisfy the predetermined criteria, the torque of the motor must exceed a predetermined torque value for a predetermined amount of time. The predetermined torque value is large enough to indicate that the media sheet S has encountered the resistance along the media path  32  associated with the media sheet&#39;s S arrival at the entrance to the feed nip  37 . However, the predetermined torque value is lower than the torque value typically associated with a motor stall. This ensures that the motor does not stall as a result of the media sheet&#39;s contact with the feed nip  37 . 
     While the exemplary embodiments include predetermined criteria comprising an increase in input voltage to the motor, increase in torque of the motor, and decrease in roller velocity, any suitable performance attribute and associated criteria may be utilized which indicates that the media sheet S has arrived at the entrance to the feed nip  37 . The satisfaction of the predetermined criteria for each page allows the imaging device  10  to automatically compensate for variables such as variation between devices and changes over the life of the device. 
     At  204 , after the performance attribute of the component of the imaging device  10  satisfies the predetermined criteria, the media sheet S is entered into the feed nip  37  in a substantially deskewed alignment. Satisfaction of the predetermined criteria confirms that the media sheet S is advanced all the way to the entrance to the feed nip  37 . When the media sheet S arrives at the feed nip  37 , the feed rollers  37   a  and  37   b  are stopped or rotating toward the entrance to the duplex path  50  thereby preventing the media sheet S from entering the feed nip  37 . The media sheet S is advanced until the leading edge of the media sheet S is flush with the entrance to the feed nip  37  thereby ensuring that the media sheet S will enter the feed nip  37  in a substantially deskewed alignment. The predetermined criteria is then satisfied. After satisfaction of the predetermined criteria, the feed rollers  37   a  and  37   b  begin to rotate in the direction of movement along the simplex path  34 , advancing the media sheet S through the feed nip  37 . Satisfaction of the predetermined criteria also ensures that the amount of slip and motion loss is not overestimated. If the slip or motion loss is overestimated the roller R will rotate for an excessive amount of time which may cause wear to the roller R and, in some instances, unpleasant noise. Embodiments include those wherein after the performance attribute of the component of the imaging device  10  satisfies the predetermined criteria, the speed of the roller R is altered. The roller R can be slowed, or in some instances stopped, because once the media sheet S passes through the feed nip  37  the feed roller  37   a , as opposed to the roller R, will advance the media sheet S. 
     One skilled in the art will understand that the foregoing method is suitable for use in embodiments and alternatives other than those illustrated in the figures such as instances where it is desirable to advance a media sheet along a media path to a feed nip and to enter the media sheet into the feed nip in a substantially deskewed alignment. For example, the foregoing method may be applied to an ADF scanner  14  in order to ensure that a media sheet traveling through the automatic document feed enters feed rollers in a substantially deskewed alignment. Further, the first method, depicted in  FIG. 8 , may be used in isolation or in combination with the second method, depicted in  FIG. 9 . Similarly, the second method, depicted in  FIG. 9 , is suitable for use in isolation but may also be used in combination with the first method, depicted in  FIG. 8 . 
     The foregoing description of several methods and an embodiment of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.