Patent Publication Number: US-2007102873-A1

Title: Apparatus for varying pressure roll nip force

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
      None.  
     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 media feed mechanisms, and more particularly to a media feed mechanisms in printing and/or scanning mechanisms.  
      2. Description of the Related Art  
      All-in-one machines typically perform functions such as printing, scanning, copying, and faxing in either a stand alone fashion or in conjunction with a personal computer and define a growing market for peripheral devices. These devices eliminate clutter in a business or home office by combining the desirable functionality of various machines into a single unit, while maintaining an affordable cost. Various all-in-one machines currently in the marketplace use thermal inkjet technology as a means for printing received fax documents, original documents, and copied or scanned images or text. Thermal inkjet printing devices utilize consumable inkjet cartridges in fluid communication with a printhead to record text and images on a print media. The printhead typically moves on a carriage relative to the media path and a control system activates the printhead to selectively eject ink droplets onto the print media.  
      Scanners are used to scan a target image and create scanned image data which can be displayed on a computer monitor, used by a computer program, can be printed, or can be faxed, etc. Scanned data may be saved to memory or a magnetic or optical drive, or other fixed or removable memory device. Scanning devices may be packaged in a stand-alone housing or as part of the all-in-one device, as described herein, including a printing module to perform scanning as well as standard copying functions.  
      Scanners typically include a housing aperture defined by an edge wherein a platen is located. A target document is positioned on the platen for scanning of the text or image by a scanbar. Depending on the positioning of the scanbar relative to the platen, the platen may be transparent where the scanbar is beneath the platen or may be solid where the scanbar is above the platen. For a typical flatbed scanner, the scanbar will be below the platen, which will have a transparent section to allow for the scan operation.  
      The scanner may also include an automatic document feeder (ADF) to automatically and sequentially feed a plurality of documents to a scan module. The ADF typically comprises a feed tray and an input device which feeds a single sheet from the stack of media on the feed tray into the ADF media path. The single sheet of media passes the reading position where the media is illuminated and image data is created by the scanbar representing images on the media. The media then passes from the ADF to a stacking tray where the media remains until all of the media from the feed tray has been scanned and is removed from the stacking tray at the output side of the ADF.  
      In either printing or ADF scanning, a printing medium or original document is transported by a feeding mechanism. The transport mechanism includes at least a pressure roller and a feed roll or driving roll. The pressure roll or idler roll forces the media against the feed roll during ADF scanning or printing. When in contact with the feed roll, the media is advanced for printing or scanning before engaging an exit roll. Prior art devices place a constant and continuous bias on the pressure roller in order to maintain engagement of the pressure roller and feed roll.  
      For ease of description, the following is directed to a printing mechanism such as an ink-jet printing operation, however, one of ordinary skill in the art should understand that the problems associated with prior art transport mechanism may also be associated with ADF scanners. When the media trailing edge exits the nip between the feed roll and the pressure roll, the media is urged forward in a feed direction. This advancement of the media occurs because a downward force of the pressure roller causes a tangential force having a component in the direction of media feed. The media may advance some undesirable distance corresponding to the backlash of a gear train driving the feed roller. The result is that media may advance some distance greater than the intended amount. The problem worsens when thicker media is utilized. Due to the over-advancement of the media, the printhead is moved from its intended position relative to the medium resulting in ink droplets being deposited inconsistently and reduced print quality. For example, banding may occur which is undesirable. In the case of ADF scanning, the media jump can result in scanning quality defects.  
      Given the foregoing, it will be appreciated that an apparatus is needed which varies the force applied to media trailing edge moving through a feed nip of a printing or scanning feedpath to eliminate media jump.  
     SUMMARY OF THE INVENTION  
      The present invention inhibits media jump when media exits the nip between the pressure roll and the feed roll.  
      According to a first embodiment, an apparatus for varying nip pressure in a media feedpath including a feed roller and a pressure roller defining a feed nip therebetween, comprises a rotatable cam having a preselected eccentric path when rotated, a first pivotable linkage pivotally engaging the rotatable cam, a second pivotable linkage, a biasing member operably interconnecting the first and second pivotal linkages for providing a biasing force on the pressure roller. The pressure roller is rotatably connected to the second linkage opposite the biasing member, wherein rotation of the cam varies the biasing force provided by the biasing member on the pressure roller. The cam has an eccentric shape. A rotatable shaft is operably connected to the cam. The first linkage pivots about a first linkage pivot point as the cam rotates. The cam loads and unloads the biasing member connected to the first linkage and the second linkage as the cam is rotated. The pressure roller exerts greater force on the feed roll as the biasing member is loaded and exerts lesser force on the feed roll as the biasing member is unloaded. The pressure roller comprises a plurality of pressure rollers.  
      According to a second embodiment, a variable pressure roll linkage for media feedpath comprises an elastic member, a first linkage, a feed drive roller and a pressure roller defining a nip therebetween, a second linkage with the pressure roller operably connected to the second linkage with the first linkage connected to the second linkage by the elastic member, a cam moveable about a preselected profile engages the first linkage wherein movement of the cam loads and unloads the elastic member and causes translation of the pressure roller at the nip. The pressure roller is translatable toward and away from the feed drive roller. Rotation of the cam pivots the first linkage. The elastic member further comprises a spring. The application of tension to the elastic member increases force of the pressure roll toward the drive roll. The application of tension is caused by movement of said cam. The pressure roll further comprises a plurality of pressure rolls mounted on a pressure roll shaft and the drive roller comprises at least one drive roller mounted on a drive roll shaft.  
      According to a third embodiment, a pressure roll linkage for applying variable pressure to a pressure roll comprises a pivotable follower plate, the follower plate is engaged by a mover to cause pivotal movement of said follower plate, a pressure roller housing is adjacent the follower plate, the pressure roller housing has at least one pressure roller; a biasing member has a first portion and a second portion, the first portion is connected to the follower plate and the second portion is connected to the pressure roller housing; wherein actuation of the mover varies pressure applied by the pressure roller. The follower plate pivots in a first direction and the pressure roller housing pivots in a second opposite direction when loading the biasing member. The pressure roller moves toward and away from a drive roll when the mover is actuated and deactuated. The biasing member is a spring which is tensioned and untensioned as the mover is actuated and deactuated. The linkage is positioned in a printer feedpath. Alternatively, the linkage may be positioned in a scanner auto-document feeder feedpath. The mover may be an eccentric cam.  
      According to a fourth embodiment, a variable force pressure roll linkage comprises a media feedpath, a drive roller located along the media feedpath, a biasable idler roller rotatably disposed opposite and biased toward the drive roller and forming a nip therebetween for feeding media, and, a variable force means which decreases biasing force on the idler roller during media exit from the nip.  
      According to a fifth embodiment, a variable force pressure roll linkage comprises a media feedpath, a drive roller located along the media feedpath, an idler roller disposed opposite and biased toward the drive roller, a first linkage and a second linkage connected by a biasing member, the idler roller rotatably connected to the second linkage; and, motion means operably coupled to the first linkage for varying force on the idler roller during media feed.  
      The present invention allows for varying of force on a pressure roller when a media trailing edge passes a feed nip thereby inhibiting media jump and printing and scanning degradation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above-mentioned and other features and advantages of this 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 all-in-one device with printing component and a scanning component;  
       FIG. 2  is a perspective view of the all-in-one device of  FIG. 1  with a cut-away section depicting the printing components;  
       FIG. 3  is a side view of a printing feedpath including an apparatus for varying pressure roll nip force;  
       FIG. 4  is a perspective view of the apparatus for varying pressure roll nip force;  
       FIG. 5  is a side view of the printing feed path and apparatus of  FIG. 3  in a second position;  
       FIG. 6  is a perspective view of the apparatus in the second position shown in  FIG. 5 ;  
       FIG. 7  is a perspective view of an alternative all-in-one device with a C-shaped printing feedpath;  
       FIG. 8  is a side view of the print feedpath of  FIG. 7 ; and,  
       FIG. 9  is a side schematic view of a scanner auto-document feeder having an apparatus for varying pressure roll nip force. 
    
    
     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. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software. As such, it should be noted that a plurality of hardware and software-based devices, as well as a plurality of different structural components may be utilized to implement the invention. Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative mechanical configurations are possible.  
      The term image as used herein encompasses any printed or digital form of text, graphic, or combination thereof. The term output as used herein encompasses output from any printing device such as color and black-and-white copiers, color and black-and-white printers, and all-in-one devices that incorporate multiple functions such as scanning, copying, and printing capabilities in one device. Such printing devices may utilize ink jet, dot matrix, dye sublimation, laser, and any other suitable print formats. The term button as used herein means any component, whether a physical component or graphic user interface icon, that is engaged to initiate output.  
      Referring now in detail to the drawings, wherein like numerals indicate like elements throughout the several views, there are shown in  FIGS. 1-9  various aspects of an apparatus for varying nip pressure in a media feedpath. The apparatus provides various functions including varying pressure roll force to decrease nip pressure and therefore substantially eliminate media jump. The apparatus may be utilized with printing components as well as ADF scanners.  
      Referring initially to  FIG. 1 , an all-in-one device  10  is shown having an ADF scanner portion  12  and a printer portion  20 , depicted generally by the housing. The all-in-one device  10  is shown and described herein, however one of ordinary skill in the art will understand upon reading of the instant specification that the present invention may be utilized with a stand alone printer, copier, ADF scanner, or other device utilizing a media feed system. The peripheral device  10  further comprises a control panel  11  having a plurality of buttons for making selections. The control panel  11  may include a graphics display to provide a user with menus, choices or errors occurring with the system.  
      Still referring to  FIG. 1 , extending from the printer portion  20  are an input tray  22  at the rear of the device  10  and an exit tray  24  extending from the front of the device  10 . A media feedpath  21  ( FIG. 3 ) extends between the input tray  22  and output tray  24 . The printer portion  20  may include various types of printing mechanisms including a laser printing mechanism or an ink-jet printing mechanism. For ease of description, the exemplary printer portion  20  is an inkjet printing device.  
      Referring now to  FIG. 2 , an interior cut-away perspective view of the all-in-one device  10  is depicted. With the interior shown, the printing portion  20  includes a carriage  26  having a position for placement of at least one print cartridge  28 .  FIG. 2  depicts two print cartridges  28  which may be, for instance, a color cartridge for photos and a black cartridge for text printing. As one skilled in the art will recognize, the color cartridge may include three inks, i.e., cyan, magenta and yellow inks. Alternatively, in lower cost machines, a single cartridge may be utilized wherein the three inks, i.e., cyan, magenta and yellow inks are simultaneously utilized to provide the black for text printing or for photo printing. During advancement media moves from the input tray  22  to the output tray  24  in a substantially L-shaped path along the media feedpath  21  beneath the carriage  26  and cartridges  28 . As the media moves into a printing zone, the media moves in a Y-direction as depicted and the carriage  26  and the cartridges move in an X-direction which, is transverse to the movement of the media M.  
      Referring again to  FIG. 1 , the scanner portion  12  generally includes an ADF scanner  30 , a scanner bed  17  and a lid  14  which is hingedly connected to the scanner bed  17 . Beneath the lid  14  and within the scanner bed  17  may be a transparent platen for placement and support of target or original documents for manually scanning. Along a front edge of the lid  14  is a handle  15  for opening of the lid  14  and placement of the target document on the transparent platen (not shown). Adjacent the lid  14  is an exemplary duplexing ADF scanner  30  which automatically feeds and scans stacks of documents which are normally sized, e.g. letter, legal, or A4, and suited for automatic feeding. Above the lid  14  and adjacent an opening in the ADF scanner  30  is an ADF input tray  18  which supports a stack of target media or documents for feeding through the auto-document feeder  30 . Beneath the input tray  18 , the upper surface of the lid  14  also functions as an output tray  19  for receiving documents fed through the ADF scanner  30 .  
      Beneath the ADF scanner  30  is an optical scanning unit having a plurality of parts which are not shown but generally described herein. The scanning unit may comprise a scanning motor and drive (not shown) which connects the scanning motor and a scanbar  280 , shown generally in  FIG. 9 . The scanbar  280  is driven bi-directionally along a scanning axis extending in the direction of the longer dimension of a scanner bed. At least one guide bar may be disposed within the scanner bed  17  and may extend in the direction of the scanning axis to guide the scanning bar  280  along the scanning axis. The scanbar  280  moves along the at least one guide bar within the scanner bed  17  beneath the platen. The scanbar  280  has a length which extends in the shorter dimension of the scanning bed. Thus, the scanbar  280  extends across one dimension and moves in a perpendicular dimension to scan an entire surface area of the platen during flatbed scanning. Further, the scanbar  280  may be positioned beneath an ADF window for scanning documents fed through the ADF.  
      The scanbar  280  may include a lamp, an image sensor, and a mirror therein for obtaining a scanned image from a document. The image sensor may be an optical reduction type image sensor or a contact image sensor (CIS) as is known in the art. In either event, the image sensor then determines the image and sends data representing the image to onboard memory, a network drive, or a PC or server housing, a hard disk drive or an optical disk drive such as a CD-R, CD-RW, or DVD-R/RW. Alternatively, the original document may be scanned by the optical scanning component and a copy printed from the printer portion  20  in the case of a multi-function peripheral device  10 . The scanbar  280  is generally either an optical reduction type using a combination of lens, mirror and a CCD (Charge Coupled Device) array or CIS array. The CCD array is a collection of tiny, light-sensitive diodes, which convert photons into electrons. These diodes are called photosites—the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site. The image of the document that is scanned using a light source such as a fluorescent bulb reaches the CCD array through a series of mirrors, filters and lenses. The exact configuration of these components will depend on the model of scanner. Some optical reduction scanners use a three pass scanning method. Each pass uses a different color filter (red, green or blue) between the lens and CCD array. After the three passes are completed, the scanner software assembles the three filtered images into a single full-color image. Most optical reduction scanners use the single pass method. The lens splits the image into three smaller versions of the original. Each smaller version passes through a color filter (either red, green or blue) onto a discrete section of the CCD array. The scanner software combines the data from the three parts of the CCD array into a single full-color image.  
      In general, for inexpensive flatbed scanners CIS arrays are used in the scanbar. CIS arrays replace the CCD array, mirrors, filters, lamp and lens with an array of red, green and blue light emitting diodes (LEDs) and a corresponding array of phototransistors. The image sensor array consisting of 600, 1200, 2400 or 4800 LEDs and phototransistors per inch (depending on resolution) spans the width of the scan area and is placed very close to the glass plate upon which rest the image to be scanned. Another version of the CIS uses a single set of red, green and blue LEDS in combination with light pipes to provide illumination of the material to be scanned. When the image is scanned, the LEDs combine to provide a white light source. The illuminated image is then captured by the row of sensors. CIS scanners are cheaper, lighter and thinner, but may not provide the same level of quality and resolution found in most optical reduction scanners. Color scanning is done by illuminating each color type of LED separately and then combining the three scans.  
      Referring now to  FIGS. 3-4 , exemplary internal components of a print feedpath  21  of the all-in-one device  10  are depicted in a side schematic view and perspective view, respectively. Media M is disposed in the input tray  22 , which is the beginning of the feedpath  21  extending to the exit tray  24  where media M is collected after printing. A frame  52  is located within the housing of the all-in-one device  10  is depicted generally and extends vertically adjacent the variable pressure roll linkage  50 . The frame  52  may include the printer frame or some other fixed structure within the all-in-one device  10  which is generally fixed relative to other moving parts. Extending through the frame  52  is a cam shaft  54 . Operably connected to the cam shaft  54  is a cam  58  which either rotates with and/or rotates about the cam shaft  54 . The cam  58  is generally round in shape but may take various geometric shapes which provides the function described further herein. The cam  58  is rotatably connected to the cam shaft  54  so that it rotates along a preselected eccentric profile or off center manner so that the rotation of the cam  58  about the pivot point  56  provides motion for linkage  50  and the pressure roll  44 . Alternatively, some device may be substituted for the cam  58 , such as a solenoid or other such mover which functions with the variable pressure roll linkage  50 .  
      Adjacent the cam  58  is a first upper linkage  60  which functions as a follower and remains engaged to the cam  58 . The first linkage  60  may comprise various shapes but is exemplarily depicted as rectangular with a first end  66  and a second end  68 . The first linkage  60  is pivotally connected at a pivot point  62  either indirectly or directly to a fixed structure, such as the frame  52 . The cam  58  engages the linkage  60  at contact point  64  and remains in contact during operation. As the cam  58  rotates, the first linkage or follower  60  moves from a normal position (shown in  FIG. 3 ) wherein the pressure roll  44  is loaded to a second position where the pressure roll  44  is generally unloaded. The cam  58  may be rotated by various components including a motor and transmission such as belt drive or gear drive. Alternatively, the cam  58  may be driven by a gear drive and motor utilized for media advancing. It should be understood by one skilled in the art that various motion means may be used to cause movement and vary pressure on the pressure roller  44 .  
      At the second end of the first linkage  60  is a biasing or elastic member  70  having a first end  72  and a second end  74 . The biasing member  70  is depicted as a coil spring but one of ordinary skill in the art will recognize that various alternative biasing devices may be utilized to connect the first linkage  60  and a second linkage  80 . The biasing member  70  is shown in its normal extended or tensioned position between the first linkage  60  and the second linkage  80 . In the normal extended position, the pressure roll  44  is biased toward the feed roll  42  and contacts the feed roll  44  unless media M is moving there between. The cam  58  may circular as shown and positioned on cam shaft  54  so that the centerline of cam  58  is not coincident with the rotational centerline of cam shaft  54  as shown in  FIG. 3 . Alternatively, cam  58  may be oval or elliptical in shape and be mounted so that its centerline is coincident with the centerline of cam shaft  54 . Either form of cam provides a preselected eccentric profile or path along which first linkage  60  travels as the cam  58  is rotated such that the pressure provided by biasing member  70  transitions from a predetermined maximum amount to a predetermined minimum amount. This can be accomplished by rotating the cam in a single direction or by reversing the direction of rotation of the cam. It should be realized that if the cam rotation is reversible that the configuration of the cam need not be circular or elliptical but may be semi-circular or semi-elliptical. The particular form and method of rotating the cam is left to the artisan.  
      The second linkage or pressure roll housing  80  is also pivotally connected to the frame  52  at pivot point  82 . The second linkage  80  has a first end  84  and a second end  86  disposed on either side of the pivot point  82 . The first end  84  is connected to the first linkage  60  by the biasing member  70 . The second end of the second linkage  86  has at least one pressure roll  44  and according to one embodiment may have a plurality of pressure rolls  44  in contact with a feed roll  42 . The contact between the feed roll  42  and the pressure roll  44  defines a nip  46  wherein media M is grasped for feeding to the printing zone beneath cartridge  28 . The pressure rolls  44  are rotatably connected to the pressure roll housing  80  so as to rotate freely with the rotation of the feed roll  42  or media M passing between the pressure and feed rollers  44 ,  42 . With the pressure rolls  42  forcing the media M into contact with the feed roll  42  as the feed roll turns, the media sheet M moves with the rotation of the feed roll  42  toward the exit system  36 . The cam  58  is shown in contact with contact point  64  of the first linkage or follower  60 . A mark “A” on the cam  58  is depicted at the contact point  64  for purpose of reference.  
      The exit system  36  comprises a driven exit roller  38  and an idler roller such as a star wheel  37 . The star wheel design is used to minimize ink degradation during media feeding and is known to one skilled in the art. The drive or exit roller  37  directs media to the exit tray  24  through a feed nip defined between the rollers  37 , 38 .  
      Referring now to  FIGS. 5-6 , the cam  58  has been rotated 180 degrees and the mark “A” is moved from its position in  FIGS. 3-4 . Accordingly, the follower  60  pivots about pivot  62  and follows the eccentric cam  58 . Because of the shape of the cam  58 , the follower  60  is positioned closer to the pivot point  56  defined by the cam shaft  54 . The follower  60  pivots about pivot point  62  at a steeper angle so that the lower end  68  of the follower  60  moves downwardly and unloads the biasing member  70 . By unloading the biasing member  70 , the force directed through the biasing member and acting on the second linkage  80  is decreased or substantially removed such that the linkage  80  pivots about pivot point  82  and so that the second end  86  of the linkage  80  moves upward. As a result, the pressure roll  44  is no longer pressed as heavily against feed roll  42  and can move away from the feed roll  42 .  
      Referring to  FIGS. 1-6 , in operation the linkage or variable force means  50  varies the force on the pressure or idler roller  44 . First, media M is positioned in the input tray  22  for feeding through the feed path  21 . The media M is advanced into the feed path  21  through the use of various components (not shown), for instance, an auto-compensating mechanism as known in the art. As the media M advances from the input tray  22  through the feed path  21  and to the nip  46 , the at least one pressure roll  44  is in contact with the feed roll  42  forcing the media M to move toward the print zone defined under the cartridge  28 . After moving through the print zone, the leading edge of media M is engaged by the exit system  36  which continues pulling the media through the print zone. As the media M continues to move through the feed nip  46  and through the print zone, the trailing edge of the media approaches the nip  46 . Simultaneously, the cam  58  begins rotation from its position shown in  FIG. 3  to its position shown in  FIG. 5 . During such rotation, the first linkage  60  pivots about its pivot point  62  toward the cam shaft  54  which in turn relieves tension on the biasing member  70 . The contact point  64  of the first linkage  60  has moved toward the first end  66  of the first linkage  60  with the rotation of the cam  58  as the tension in the biasing member  70  is relieved, and the pressure roll  44  is moved upwardly from the feed roll  42  and media M such that a space is defined therebetween. As a result, when the trailing edge of media M passes through the nip  46 , the media M is not urged toward the exit system  36  as with prior art devices. This design comprising a first linkage  60  and a spring connected second linkage  80  is advantageous because rotation of the cam  58  provides a gradual movement of the second linkage  80  and roller  44 . Such gradual movement inhibits printing defects as opposed to a sudden linkage movement which can occur with the direct engagement of a cam and the second linkage or pressure roller housing  80 . Thus, the present invention utilizes a variable force on the pressure roll  44  rather than a continuous force so that the media trailing edge is not urged forwardly along the feed path toward the print cartridge  28  and exit system  36 . Further, the linkage system  50  allows for greater movement of the mover, such as the cam  58 , resulting in only slight movement of the pressure roller  44 .  
      Referring now to  FIG. 7 , an alternative embodiment of an all-in-one device  110  is depicted comprising a scanner  12  and a printer portion  120 . The scanner portion  12  comprises an auto-document feed (ADF) scanner  30  and a flat bed scanner, generally depicted at  117 . The ADF scanner  30  comprises an input tray  118  and an output tray  119 , the device further comprises a scanner bed  117  and a lid  114  attached to the scanner bed  117 . Upon opening of the lid  114 , a platen (not shown) is revealed where documents, photos or drawings may be placed for flatbed scanning. The ADF scanner  30  is preferable for use in scanning stacks of documents and other such media sizes which are appropriately sized for such automatic scanning. The printing portion  120  comprises an input tray  122  and an exit or output tray  124  disposed above the input tray and thereby defining a C-shaped printing path, as opposed to the L-shaped path of the device shown in  FIG. 1 .  
      Referring now to  FIG. 8 , a side schematic view of an exemplary C-path printing portion  120  is depicted which may be utilized in the all-in-one device  110  shown in  FIG. 7 . The side view of the printing portion  120  has some detail removed for purpose of clarity. A plurality of media M is disposed on the input tray  122  at a lower portion of the printing portion feed mechanism. Generally, the media M is picked by a paper picking mechanism, such as an auto-compensating mechanism  130  and directed upwardly into the feed path  121 . The feed path is substantially C-shaped and directs the leading edge of the media to the variable pressure roll linkage  150 . The variable pressure roll linkage  150  extends from a fixed structure  152 , such as a frame, and comprises a cam  158  which rotates about a cam shaft  154  to move a first linkage  160  that pivots about pivot point  162  and causes variable loading of a biasing member  170 . By loading and unloading the biasing member  170  a second linkage  180  pivots at pivot point  182  causing application of force at the pressure roll  144  against the feed roll  142 . As previously described, as the trailing edge of a media sheet approaches the nip  146  defined between the pressure roll  144  and the feed roll  142 , the cam  158  is rotated about its pivot point  156  so as to untension the biasing member  170  and cause the pressure roll  144  to move away from the feed roll  142 . With the pressure roll  144  not applying pressure to the media, the media jump which causes printing degradations is removed. As previously noted, the leading edge of the media is engaged by the exit system  136  before the pressure roll  144  completely disengages the media M so that the media is pulled through the print zone by the exit system  136 . Thus, when the pressure roll  144  disengages from the feed roll  142 , the media maintains its advancement through the printer feed path  121 . This media disengagement point with the feed roll  142  can be sensed, using a flag or other means as is known in the art for position sensing, and the force on the pressure rolled can be increased either to the maximum amount of pressure available or some intermediate amount of pressure by rotating cam  158  prior to the arrival of the next sheet of media at the feed roller  142 . Conversely, the pressure at nip  146  can be increased after arrival of the next sheet of media at feed roller  142  is sensed.  
      Referring now to  FIG. 9 , a side schematic view of the ADF scanner  30  is depicted which may be utilized in either all-in-one device  10 ,  110  ( FIGS. 1 and 7 ) or in a standalone capacity. The ADF scanner  30  is depicted including various portions of the feedpath  221  as well. A pick system  233  is shown disposed above the input tray  18  for moving an uppermost media sheet from a media stack into the feedpath  221 . The pick system  233  may comprise an auto-compensating mechanism, as known in the art, or may comprise alternate media picking components. Near the entrance portion of the feedpath  221  is a delivery system  230  which receives media moved by the pick or input system  233 . The delivery system  230  comprises at least one delivery drive roller  232  and at least one delivery idler roller  234 . A motor and gear train or other transmission (not shown) cause rotation of the delivery drive roller  232  for feeding the media M along feedpath  221 . The delivery idler roller  234  includes at least one roller that rotates freely on an idler shaft  237 . The at least one delivery idler roller  234  is biased toward the at least one delivery drive roller  232  by a biasing member (not shown), such as a leaf spring to form a nip  235  between the delivery drive roller  232  and the delivery idler roller  234 . The delivery system  230  receives media M picked by the pick system  233  and feeds the media M through the feedpath  221  to a feed system  240 .  
      The feed system  240  comprises a feed drive roller  242  and an opposed feed pressure roller  244 . A motor and gear train or other transmission (not shown) cause rotation of the feed drive roller  242  for feeding the media M along feedpath  221 . The feed pressure roller  244  is biased toward the feed drive roller  242  defining a nip  246  therebetween which receives media M from the delivery system  230  and directs the media M across a scanning station  280 . The pressure roller  244  is biased toward the feed drive  242  by a variable force pressure roll linkage  250 , as previously described. Accordingly, a rotatable cam  258  or motion device operably mounted on cam shaft  254  causes movement of a pivotable follower or first linkage  260  that pivots about pivot point  262  on frame  252  and which is connected to the pressure roller  264  via a biasing member  270  and second pivotable linkage  280  that pivots about pivot point  282  on frame  252 . As the biasing member  270  is tensioned the pressure roller  244  engages the drive roller  242 . When the biasing member  70  is unbiased, the pressure roller  244  moves away from the feed drive roller  242 . Rotation of the cam  258  causes the increase or decrease in the amount of pressure exerted by the pressure roller  244  on the feed drive roller  242  at the nip  246 .  
      Between the feed system  240  and the exit system  336  is a scanbar  300  including a representative scanning image sensor  302  schematically depicted as a series of mirror and a sensing element. As previously discussed, media M passing through the feedpath  221  is exposed to light in order to acquire image data of the image or text on the media. The variable force pressure roll linkage  250  is useful in the present embodiment because with a feed system having a biased pressure roller at a constant pressure media M can jump as the trailing edge of media M exits through the nip of such a feed system.  
      In operation, the pick system  233  directs media M from the media tray  18  into the feedpath  221 . The media M reaches the delivery system  230  and is further directed to the feed system  240  through the feedpath  221 . The pressure roller linkage  250  is disposed in the first position to cause engagement between pressure roller  244  and the feed drive roller  242 . As the feed drive roller  242  causes advancement of the media M toward the image sensor  300  and associated scan area, the trailing edge of the media M approaches the feed system  240 . Prior to the trailing edge of the media M reaching nip  246  defined between the rollers  242 ,  244 , the linkage  250  is operated so as to vary pressure on the feed drive roller  262  by the pressure roller  264 . At this point the linkage  250  is operated so that the pressure in the nip  246  is substantially reduced or is negligible. In other words, the moving device causes actuation of the first and second linkages  260 ,  280  as well as the biasing member  270 .  
      With the various embodiments described herein after the trailing edge of the media M exits the nip, the variable pressure linkages  50 ,  150 , and  250  can be operated such that the pressure exerted by the pressure rollers  44 ,  144  and  244  at nip is increased until the desire feeding pressure is reached. This can occur prior to the leading edge of the next sheet of media M reaching nip  46 ,  146 ,  246  or it may occur after the next sheet in already within the nip. For example, it may be advantageous with thicker media to have reduced pressure at nip possibly preventing damage to the edge of the media or allowing a reduction in the amount of force need to drive such media along the media feedpath.  
      The present invention allows for varying of force on a pressure roller when a media trailing edge passes a feed nip thereby inhibiting media jump and printing and scanning degradation.  
      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.