Abstract:
A method for providing increased performance in fully active retard feeders includes driving a feed roll and retard roll pair of a reprographic apparatus backwards periodically at the start of the machine or during idle periods to compensate for contamination buildup and/or roll “set” when left in position overnight.

Description:
BACKGROUND 
       [0001]    1. Field of the Disclosure 
         [0002]    This invention relates in general to an image forming apparatus, and more particularly, to an image forming apparatus employing an improved fully active retard feeder (FAR). 
         [0003]    2. Description of Related Art 
         [0004]    In reprographic machines, an important operation involves the feeding of copy sheets. One device for accomplishing this act is a retard feeder, such as, disclosed in U.S. Pat. No. 7,464,923. It is generally accepted that a fully active retard feeder works better after the first few sheets have been fed. This may be due to heat build up in the feed rolls giving the rolls a higher coefficient of friction. Another possibility could be that due to scuffing of rolls against each other cleaning away any surface debris that would give a drop in coefficient of friction. Additionally, the rolls tend to take a “set” when left in one position overnight, but once they start to revolve this “set” is eliminated. A problem with the FAR feeder is that this poor feeding of the first few sheets can lead to skipped pitches and/or misfeeds. 
         [0005]    Given that the vast majority of customer jobs run only a few pages in length, performance improvement in FAR feeders is a necessity. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0006]    Accordingly, an improved device and method for providing increased performance in FAR feeders is disclosed that comprises driving a feed roll pair of a reprographic apparatus backwards periodically at the start of the machine or during idle periods to compensate for contamination buildup and/or roll “set” when left in position overnight. 
         [0007]    The disclosed reprographic system that incorporates the disclosed FAR feeder with the improved pre and post feed cycle routines may be operated by and controlled by appropriate operation of conventional control systems. It is well-known and preferable to program and execute imaging, printing, paper handling, and other control functions and logic with software instructions for conventional or general purpose microprocessors, as taught by numerous prior patents and commercial products. Such programming or software may, of course, vary depending on the particular functions, software type, and microprocessor or other computer system utilized, but will be available to, or readily programmable without undue experimentation from, functional descriptions, such as, those provided herein, and/or prior knowledge of functions which are conventional, together with general knowledge in the software of computer arts. Alternatively, any disclosed control system or method may be implemented partially or fully in hardware, using standard logic circuits or single chip VLSI designs. 
         [0008]    The term ‘printer’ or ‘reproduction apparatus’ or ‘reprographic device’ as used herein broadly encompasses various printers, copiers or multifunction machines or systems, xerographic or otherwise, unless otherwise defined in a claim. The term ‘sheet’ herein refers to any flimsy physical sheet or paper, plastic, or other useable physical substrate for printing images thereon, whether precut or initially web fed. 
         [0009]    As to specific components of the subject apparatus or methods, or alternatives therefore, it will be appreciated that, as is normally the case, some such components are known per se&#39; in other apparatus or applications, which may be additionally or alternatively used herein, including those from art cited herein. For example, it will be appreciated by respective engineers and others that many of the particular components mountings, component actuations, or component drive systems illustrated herein are merely exemplary, and that the same novel motions and functions can be provided by many other known or readily available alternatives. All cited references, and their references, are incorporated by reference herein where appropriate for teachings of additional or alternative details, features, and/or technical background. What is well known to those skilled in the art need not be described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Various of the above-mentioned and further features and advantages will be apparent to those skilled in the art from the specific apparatus and its operation or methods described in the example(s) below, and the claims. Thus, they will be better understood from this description of these specific embodiment(s), including the drawing figures (which are approximately to scale) wherein: 
           [0011]      FIG. 1  is a frontal view of an exemplary xerographic printer that includes the improved friction retard feeder apparatus; and 
           [0012]      FIG. 2  is an exploded, partial schematic side view of a one embodiment of the retard sheet feeder apparatus that includes the improved pre and post feed routines. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    While the disclosure will be described hereinafter in connection with a preferred embodiment thereof, it will be understood that limiting the disclosure to that embodiment is not intended. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the disclosure as defined by the appended claims. 
         [0014]    For a general understanding of the features of the disclosure, reference is made to the drawings. In the drawings, like reference numerals have been used throughout to identify identical elements. 
         [0015]    Referring to  FIG. 1  of the drawings, an original document is positioned in a document handler  27  on a raster input scanner (RIS) indicated generally by reference numeral  28 . The RIS contains document illumination lamps, optics, a mechanical scanning drive and a charge couple device (CCD) array. The RIS captures the entire original document and converts it to a series of raster scan lines. This information is transmitted to an electronic subsystem (ESS) which controls a raster output scanner (ROS) described below. 
         [0016]      FIG. 1  schematically illustrates an electrophotographic printing machine which generally employs a photoconductive belt  10 . Preferably, the photoconductive belt  10  is made from photoconductive material coated on a ground layer, which, in turn, is coated on an anti-curl backing layer. Belt  10  moves in the direction of arrow  13  to advance successive portions sequentially through the various processing stations disposed about the path of movement thereof. Belt  10  is entrained about stripping roller  14 , tensioning roller  20  and drive roller  16 . As roller  16  rotates, it advances belt  10  in the direction of arrow  13 . 
         [0017]    Initially, a portion of the photoconductive surface passes through charging station A. At charging station A, a corona generating device indicated generally by the reference numeral  22  charges the photoconductive belt  10  to a relatively high, substantially uniform potential. 
         [0018]    At an exposure station, B, a controller or electronic subsystem (ESS), indicated generally by reference numeral  29 , receives the image signals representing the desired output image and processes these signals to convert them to a continuous tone or grayscale rendition of the image which is transmitted to a modulated output generator, for example, the raster output scanner (ROS), indicated generally by reference numeral  30 . Preferably, ESS  29  is a self-contained, dedicated minicomputer. The image signals transmitted to ESS  29  may originate from a RIS as described above or from a computer, thereby enabling the electrophotographic printing machine to serve as a remotely located printer for one or more computers. Alternatively, the printer may serve as a dedicated printer for a high-speed computer. The signals from ESS  29 , corresponding to the continuous tone image desired to be reproduced by the printing machine, are transmitted to ROS  30 . ROS  30  includes a laser with rotating polygon mirror blocks. The ROS will expose the photoconductive belt to record an electrostatic latent image thereon corresponding to the continuous tone image received from ESS  29 . As an alternative, ROS  30  may employ a linear array of light emitting diodes (LEDs) arranged to illuminate the charged portion of photoconductive belt  10  on a raster-by-raster basis. 
         [0019]    After the electrostatic latent image has been recorded on photoconductive surface  12 , belt  10  advances the latent image to a development station, C, where toner, in the form of liquid or dry particles, is electrostatically attracted to the latent image using commonly known techniques. The latent image attracts toner particles from the carrier granules forming a toner powder image thereon. As successive electrostatic latent images are developed, toner particles are depleted from the developer material. A toner particle dispenser, indicated generally by the reference numeral  44 , dispenses toner particles into developer housing  46  of developer unit  38 . 
         [0020]    With continued reference to  FIG. 1 , after the electrostatic latent image is developed, the toner powder image present on belt  10  advances to transfer station D. A print sheet  48  is advanced to the transfer station, D, by a sheet fully active retard feeding apparatus,  50 . Preferably, sheet feeding apparatus  50  includes a nudger roll  51  which feeds the uppermost sheet of stack  54  to a nip formed by feed roll  52  and a retard roll  53 . Retard roll  53  is mounted on shaft  91  and controlled by controller  29  through a conventional clutch, such as, a wrap spring clutch as disclosed in U.S. Pat. No. 3,905,458. Feed roll  52  rotates to advance the sheet from stack  54  into vertical transport  18 . Vertical transport  18  directs the advancing sheet  48  of support material into the registration transport  120  which, in turn, advances the sheet  48  past image transfer station D to receive an image from photoconductive belt  10  in a timed sequence so that the toner powder image formed thereon contacts the advancing sheet  48  at transfer station D. Transfer station D includes a corona generating device  47  which sprays ions onto the back side of sheet  48 . This attracts the toner powder image from photoconductive surface  12  to sheet  48 . The sheet is then detacked from the photoreceptor by corona generating device  49  which sprays oppositely charged ions onto the back side of sheet  48  to assist in removing the sheet from the photoreceptor. After transfer, sheet  48  continues to move in the direction of arrow  60  by way of belt transport  62 , which advances sheet  48  to fusing station F. 
         [0021]    Fusing station F includes a fuser assembly indicated generally by the reference numeral  70 , which permanently affixes the transferred toner powder image to the copy sheet. Preferably, fuser assembly  70  includes a heated fuser roller  72  and a pressure roller  74  with the powder image on the copy sheet contacting fuser roller  72 . The pressure roller is cammed against the fuser roller to provide the necessary pressure to fix the toner powder image to the copy sheet. The fuser roll is internally heated by a quartz lamp (not shown). Release agent, stored in a reservoir (not shown), is pumped to a metering roll (not shown). A trim blade (not shown) trims off the excess release agent. The release agent transfers to a donor roll (not shown) and then to the fuser roll  72 . 
         [0022]    The sheet then passes through fuser  70  where the image is permanently fixed or fused to the sheet. After passing through fuser  70 , a gate  80  either allows the sheet to move directly via output  84  to a finisher of stacker, or deflects the sheet into the duplex path  100 , specifically, first into single sheet inverter  82  here. That is, if the sheet is either a simplex sheet or a completed duplex sheet having both side one and side two images formed thereon, the sheet will be conveyed via gate  80  directly to output  84 . However, if the sheet is being duplexed and is then only printed with a side one image, the gate  80  will be positioned to deflect that sheet into the inverter  82  and into the duplex loop path  100 , where that sheet will be inverted and then fed to acceleration nip  102  and belt transport  110 , for recirculation back through transport station D and fuser  70  for receiving and permanently fixing the side two image to the backside of that duplex sheet, before it exits via exit path  84 . 
         [0023]    After the print sheet is separated from photoconductive surface  12  of belt  10 , the residual toner/developer and paper fiber particles adhering to photoconductive surface  12  are removed therefrom at cleaning station E. Cleaning station E includes a rotatably mounted fibrous brush in contact with photoconductive surface  12  to disturb and remove paper fibers and a cleaning blade to remove the non-transferred toner particles. The blade may be configured in either a wiper or doctor position depending on the application. Subsequent to cleaning, a discharge lamp (not shown) floods photoconductive surface  12  with light to dissipate any residual electrostatic charge remaining thereon prior to the charging thereof for the next successive imaging cycle. 
         [0024]    The various machine functions are regulated by controller  29 . The controller is preferably a programmable microprocessor that controls all of the machine functions hereinbefore described. The controller provides a comparison count of the copy sheets, the number of documents being recirculated, the number of documents being recirculated, the number of copy sheets selected by the operator, time delays, jam corrections, receive signals from full width or partial width array sensors and calculate skew in sheets passing over the sensors, calculate the change in skew, the speed of the sheet and an overall comparison of the detected motion of sheets with a reference or nominal motion through a particular portion of the machine. 
         [0025]    Fully active retard sheet separator/feeder  50  is a friction retard top sheet feeder that will now be described with particular reference to  FIG. 2 . Sheets  48  are fed from a stack by nudger roll  51  which engages the top sheet in the stack and on rotation feeds the top sheet towards a nip formed between separation or feed roll  52  and retard roll  53 . Feeding from tray  54  by nudger roll  51  is obtained by creating a stack normal force (e.g., of 1.5 Newtons) between the nudger roll and the paper stack. This force is achieved by the weight of the nudger wheel and its associated components acting under gravity. 
         [0026]    At the beginning of a print cycle, the machine logic will interrogate the system to determine if any paper is in the paper path. If there is no paper in the paper path, the logic will initiate a signal to a feed clutch in nudger  51 , thereby starting the feeder. The nudger roll  51  will drive the top sheet of paper  48  into the nip between feed roll  52  and retard roll  53 . Microswitch  57  indicates when a sheet has been forwarded by the nudger roll. As the feed roll rotates, it drags a sheet of paper from the stack. Frictional forces and static electricity between the sheets of paper in the stack may cause several sheets to move into the nip together. 
         [0027]    If several sheets of paper approach the nip together, the friction between the retard roll  53  and the bottom sheet of those being fed is greater than that between two sheets. The friction between the feed roll  52  and the top sheet  51  is greater than the friction between two sheets. The group of sheets being fed towards the nip will therefore tend to become staggered around the curved surface of the retard roll up into the nip, until the lower sheet S 2  of the top two sheets is retained by the retard roll  53 , while the topmost sheet is fed by the feed roll  52 . Of course, in order for this to happen, the friction between the feed roll  52  and a paper sheet must be greater than the friction between a paper sheet and the retard roll  53 . Therefore, the feed roll  52  drives the top sheet  51  away from the stack and the next sheet S 2  is retained in the nip to be fed next. Microswitch  58  communicates to controller  29  whether a sheet has reached that point in feeding. 
         [0028]    The feed clutch remains energized until paper is sensed by the input microswitch  59 . Paper, whose leading edge has reached this switch  59 , is under the control of the takeaway rolls  55 ,  56  that drive the sheet towards registration transport  120  shown in  FIG. 1 . 
         [0029]    In order to prevent misfeeds and/or skipped pitches during feeding and in accordance with the present disclosure, prior to feeding, a motor drivingly connected to feed roll  52  and retard roll  53  is turned ON and the retard roll is driven in a reverse direction to paper feed. The drive of retard roll  53  will cause feed roll  52  to drive in the opposite direction as it slips on a one-way clutch. As the feed and retard roll are driving in the reverse direction, the nudger roll  51  will remain motionless. Any paper in the vicinity of the nip between feed roll  52  and retard roll  53  will either remain motionless or will be driven in reverse back to the stack  54 . The motion of the retard roll drive will warm, clean and de-flat the retard and feed rolls. This will prepare the two components in readiness for feeding a sheet of paper out of stack  54 . 
         [0030]    In addition to or alternatively, the feed roll and retard roll pair  52 ,  53  are periodically rotated backwards at predetermined times during idle periods of the machine to alleviate contamination built-up and/or roll “set”. 
         [0031]    It should now be understood that a FAR paper feed system has been disclosed which employs a feed roll pair that is driven backward periodically prior to an initial feeding sequence and/or during idle periods of the machine to alleviate contamination built-up and roll “set”. In view of the fact that the vast majority of customer jobs are only a few pages, this technique represents a big improvement over present FAR feeders. Various events are contemplated that could trigger the disclosed procedures for “de-flatting” the drive and retards rolls including, for example, time, humidity, temperature, roll materials, etc. 
         [0032]    The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others. Unless specifically recited in a claim, steps or components of claims should not be implied or imported from the specification or any other claims as to any particular order, number, position, size, shape, angle, color, or material.