Patent Application
20070102873
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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.
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.
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:
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
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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
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.
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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
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
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.
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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.
