Patent Application
20070102871
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1.Field of the Invention
The present invention relates generally to media feed mechanisms, and more particularly to inhibiting media nip jump and rollback induced banding at the exit shaft.
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.
The all-in-one devices utilize feed mechanisms configured to move sheets sequentially from the input tray, through a printing component and to an exit tray. Thus, feed mechanisms may include many parts which provide for media movement. Many feed mechanisms include drive transmissions which convert motor rotation into roller and shaft rotation to move media through the media path. The media is advanced in preselected steps or distances, also known as indexing, in order to properly form a printed image. Typically, these drive transmissions are gear drives, which require a necessary amount of tooth clearance, called backlash, for proper operation. Backlash is the amount of clearance between mated gear teeth in a gear pair. When media is passing through the printing component, any unintended advancement of media may result in print defects, such as banding or the like. Unfortunately, since proper gear design requires some backlash, unintended media movement is a continual problem. Some backlash is required to allow for lubrication, manufacturing errors, deflection under load and differential expansion between the gears and the housing. Backlash is created when the tooth thickness of either gear is less than the tooth thickness of an ideal gear, or the zero backlash tooth thickness. For example, standard practice is to make allowance for half the backlash in the tooth thickness of each pair.
During media feeding, at least two phenomenon may cause a printing defect known as banding. The first phenomenon that causes print banding is called media nip jump. When a media trailing edge exits a feed nip between a feed roll and the pressure or idler roll, the media is urged forward in a feed direction. This is due to the downward force of the biased idler roll stepping down from the media surface over the media trailing edge. Specifically, the downward force of the pressure roller causes a component force in the direction of media feed. The phenomenon is more pronounced when thicker media is utilized. Further, as the media disengages the feed system, the exit system becomes the sole driving force on the media. The exit system is typically overdriven, i.e. driven at a faster speed than the feed system, so that the media remains taut. This also causes media jump. The media may advance some undesirable distance corresponding to the backlash of a geartrain driving the feed roller. The result is that media may advance some distance greater than the intended amount.
The second phenomenon causing print defects is exit shaft rolling or rollback. Each time the motor rotates a preselected distance to index media through the feedpath, the motor stops. However, the exit shaft and rollers do not stop at the exact position and time that the motor stops at each indexing movement. This is due to several factors, such as the previously indicated backlash in the gear drive, commutator jump, exit system overdrive and other system tolerances. These tolerances are dampened to a large extent when the media is disposed within both the exit nip and feed nip because the feed system dampens the exit system overdrive and tolerances. However, when the media exits the feed system and is solely influenced by the exit system, the dampening effects of the feed system are lost and banding print defects are more visible to a user.
Given the foregoing, it will be appreciated that achieve benefits derived from overcoming the shortcomings and detriments described previously.
The present invention solves these problems by providing a damping structure for an exit shaft in order to minimize media jump from the media feed system.
According to a first embodiment, a damping device for a media feed mechanism having media feedpath defined between a feed shaft and a downstream exit shaft comprising a damping hub mounted on said exit shaft, and a resilient biasing member extending between the damping hub and the feed shaft to create a damping force on the damping hub. The damping hub is of a preselected diameter. The exit shaft further comprises at least one exit roller on the exit shaft. The at least one exit roller may be a plurality of exit rollers. The resilient biasing member engages a stationary component disposed between the feed shaft and the exit shaft wherein the stationary component may comprise a motor disposed between the damping hub and the feed shaft. The resilient biasing member elastically bends around the motor.
According to a second embodiment, a damping assembly for a media feedpath comprises a feedpath having a first shaft and a second shaft parallel and downstream from the first shaft, a damping hub is disposed on the second shaft, and a brake structure engages the damping hub wherein the brake structure applies torque on the damping hub to inhibit unintended movement of the second shaft during media feed. The brake structure comprises a first damping arm and a second damping arm, and the first and second damping arms extend around the damping hub. The damping assembly further comprises a biasing member engaging the brake structure and damping movement of the second shaft. The damping assembly further comprises a dampener pivot disposed adjacent the brake structure. The damping arms are pivotally connected to the dampener pivot.
According to a third embodiment, an exit shaft damping assembly for a media feedpath in a peripheral device comprises a damping assembly engaging an exit shaft along the media feedpath, the damping assembly has a damping arm and a biasing member extending from the peripheral device and engaging a damping arm, a brake connecting to the damping arm, and a damping hub extends from at least one exit roller of the exit shaft wherein the brake engages the damping hub and places a torque on the exit shaft. The brake structure further comprises an arm pivotally attached to a fixed structure in said peripheral device. The peripheral device may be a printer or an auto-document feed scanner. The biasing member may be a spring. The exit shaft damping assembly may further comprise a print zone disposed adjacent the exit shaft along the media feedpath and a print cartridge between the exit shaft and a feed shaft.
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 so-called “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 input or output.
Referring now in detail to the drawings, wherein like numerals indicate like elements throughout the several views, there are shown in
Referring initially to
Extending from the printer portion or component 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 (
Referring now to
Referring again to
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 which connects the scanning motor and a scanbar. The scanbar 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 along the scanning axis. The scanbar moves along the at least one guide bar within the scanner bed 17 beneath the platen. The scanbar has a length which extends in the shorter dimension of the scanning bed. Thus, the scanbar 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 may be positioned beneath an ADF window for scanning documents fed through the auto-document feeder where the document is moved past the scanbar. In some duplex scanning arrangements that do not turn over the scanned documents, two scanbars are provided and positioned on opposites of the document. One of the two scanbars may be moveable.
The scanbar 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 component 20 in the case of a multi-function peripheral device 10. The scanbar 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 used 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
Downstream of the feed roller 44 is an exit system 60 comprising an exit shaft 64 having a hub 68 located thereon. The hub 68 has a preselected diameter which is dependent upon the desired torque on the exit shaft 64. As will be understood by one skilled in the art, by increasing the diameter of the hub 68, the torque on the exit shaft will increase and by decreasing the diameter of the shaft 64, the torque will decrease. Connected to the exit shaft 64 is an exit gear 62 which is also driven, either directly or indirectly, by the motor 41. The exit shaft 64 is driven at a faster speed than the feed shaft 43 so that the media M remains taut. The exit shaft 64 also comprises at least one exit roller 65 which is directly beneath an exit star wheel 66. The exit roller 65 and exit star wheel 66 form a nip 67 wherein media is fed and pulled to the output tray 24. Extending between the feed roller 44 and the exit shaft hub 68 is an elastic biasing member 50.
Referring now to
In operation, media M is moved from the input tray 22 to the feed system 40 by an input system which may include an auto-compensating mechanism. As the media M advances into the feedpath 21, the leading edge of the media M reaches a nip 47 defined by an idler roller 46 and a feed roller 44 on the feed roller shaft 43. The motor 41 indexes the leading edge of the paper into a print zone 29 beneath the print cartridge 28 where ink droplets are selectively ejected onto the media to form an image, which may include text and/or a picture. As the motor 41 continues to index the media M downstream toward the exit shaft 64, the media leading edge enters a nip 67 defined between the exit star wheel 66 and an exit roller 65 on the exit shaft 64. The motor 41 continues to index the media through the exit nip 47 by causing rotation of the exit gear 62. As the trailing edge of the media M reaches the feed nip 47 between the idler roller 46 and a feed roller 44, the media M does not incur media nip jump as typical in prior art devices. Instead, the torque of the elastic biasing member 50 on the exit damping hub 68 inhibits media nip jump caused by the spring force of the idler roller 46 on the feed roller 44. Alternatively stated, the engagement of the biasing member 50 on the hub 68 inhibits movement of the exit shaft 64 caused by a lateral force component on the media M by the idler roller 46. Thus, the motor 41 continues to index the media M by driving the exit gear 62 until the media advances to the output tray 24.
Referring now to
Opposite the feed gear 142 along the feedpath 121 is an exit system 160 comprising an exit gear 162 which is also driven, directly or indirectly, by the motor 141. The exit gear 162 is positioned on a rotatable exit shaft 164, which further comprises an exit hub 168 thereon. Also disposed along the exit shaft 164 are one or more exit rollers 165 which form a nip 167 with an exit star wheel 166. The exit star wheel 166 is biased toward the exit rollers 165 to form the media exit nip 167. The nip 167 receives media passing through the print zone 129 and continues to index the media from the printer component 120 to the output tray 124.
As described in the L-shaped feedpath embodiment, an elastic biasing member 150 extends from the feed shaft 143 to the exit hub 168 and over the motor 141. The elastic biasing member 150 comprises, as shown in
In operation, the media M is directed from the input tray 122 by the auto-compensating mechanism 123 into the feedpath 121 of a C-shaped media feed path, an L-shaped shaped media feedpath or an auto-document feeding scanner. The motor 141 drives the auto-compensating mechanism 123 as well as the feed roller 144 and the exit shaft 164. As the media M moves through the C-shaped feedpath 121, the media M leading edge enters the feed nip 147. The motor 141 is controlled by a print controller (not shown) which indexes the media M through the feed nip 147, the print zone 129 and to the exit system 160. As the leading edge of media M reaches the exit system 160, the media M moves into the exit nip 167 between the exit star wheel 166 and the exit gear 162. When the trailing edge of media M passes the feed nip 147, the media exit system 160 continues indexing the media. However, the spring biased idler 146 which causes media nip jump and pushes the media forward in the feedpath 121, cannot force the media forward because the torque on the exit shaft 164 by the biasing member 150 inhibits unintended movement of the media M. Further, the application of torque by the biasing member 150 on the exit shaft 164 also inhibits rollback of the exit shaft 164. Thus, as the trailing edge of media M exits the feed nip 147, the biasing member 150 improves two sources of printing defects, i.e. media nip jump and exit shaft rollback. This structure and function provides improved results over prior art printers having printing defects such as banding and other defects.
Referring now to
In operation of the damping assembly 250 may be positioned along either an L-shaped media feedpath, a C-shaped media feedpath as previously described, or an auto-document document feeding scanner to substantially inhibit scanning defects. With the brakes 257, 259 extending about the damping hub 268 and the biasing member 272 extending between the arms 252, 254, a continuous frictional force is created between the damping hub 268 and the brakes 257, 259 when the exit shaft 264 rotates during media feeding. As the motor (not shown) rotates, the exit shaft 264 rotates in order to advance media M (
Referring now to
Along the media feedpath 321 is a feed system 340 having a feed gear 342 connected to a rotatable feed shaft 343. The feed shaft 343 further comprises at least one feed roller 344 which rotates with the feed shaft 343 and forms a nip 347 with the idler roller 346 opposite the feed roller 344. The feed gear 342 is driven, either directly or indirectly, by a motor 341. Opposite the feed system 340 along the feedpath 321 is an exit system 360 comprising an exit gear 362 which is also driven, either directly or indirectly, by the motor 341. The exit gear 362 is connected to an exit shaft 364 which comprises a damping hub 368 thereon. Also located on exit shaft 364 is an exit roller 365 which rotates with the exit shaft 364 and forms an exit nip 367 with the star wheel 366 opposite the exit roller 365. The star wheel 366 is spring biased toward the exit roller 365 to index media from the print zone 329 to the output tray 324 along media path 321.
The feed nip 347 and exit nip 367 are substantially aligned so that the media M is directed through the print zone 329 beneath the print cartridge 328 by the feed roller 344 until the media M reaches the exit nip 367 which continues to pull the media M through the print zone after the trailing edge of the media M passes through the feed nip 347.
Extending from the frame or other fixed structure of the printing component 320 is a damping assembly 350 comprising a damping arm 352 which is pivotally connected at a first end at pivot 376 to the frame or other fixed structure within the printer 320. The damping arm 352 is biased at a second opposed end by an elastic biasing member 372. The exemplary elastic biasing member 372 is a coil spring which provides a continuous force on the damping arm 352 in the direction of damping hub 368. However, alternative devices may be substituted to provide a force on the damping arm 352. Also located at the second end of the damping arm 352 is a brake 357 having a curvilinear surface that engages the damping hub 368. The curvilinear surface of the brake 357 has a radius which corresponds to the radius of the damping hub 368 so that the two pieces are frictionally engaged along the outer surface of the damping hub 368 and the curvilinear brake surface. The elastic biasing member 372 provides a continuous upwardly directed force on the damping arm 352 and therefore provides a torque on the damping hub 368 and exit shaft 364. The continuous radial force causes friction between the hub 368 and brake 357 having a dampening effect on the exit shaft 364.
In operation, an upper most media sheet M is directed from the input tray 322 by media input means, such as an auto-compensating mechanism (
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.
