Patent Application
20080073825
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 below, and the claims. Thus, they will be better understood from this description of the specific embodiment, including the drawing figures (which are approximately to scale) wherein:
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.
The disclosure will now be described by reference to a xerographic printing apparatus that includes an improved retard feeder apparatus.
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.
Referring to
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.
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.
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.
With continued reference to
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 canned 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.
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.
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.
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.
Sheet separator/feeder 50 is a semi-active friction retard top sheet feeder that will now be described with particular reference to
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.
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 S1 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 S2 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 S1 away from the stack, and the next sheet S2 is retained in the nip to be fed next. Microswitch 58 communicates to controller 29 whether a sheet has reached that point in feeding.
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.
Under normal conditions, elastomer covered retard roll 53 will rotate with a sheet during a single sheet feed. As the retard roll wears and the roll diameter decreases, the force imparted at the roll surface by the torque-limiting hysteresis clutch 86 proportionately increases. As shown in
While hysteresis clutch 86 is shown as a separate component and not integral with retard roll 53, an integral retard roll, hysteresis clutch and Hall Effect sensor in one device is within the scope of the disclosure.
It should now be understood that an improved retard paper feed system has been disclosed that employs a controllable torque device in the separation nip. The Controllable torque device is a torque-limiting hysteresis clutch 86 coupled to a retard roll. A Hall Effect sensor 95 is positioned adjacent to the outer surface of the clutch to monitor any stall by the retard roll during the feeding process which will indicate excessive wear of the retard roll. Once the sensor senses stall in the motion of the retard roll, a signal is sent to a controller which sends a signal to a graphic user interface. The graphic user interface alerts an operator to the need to order and replace the roll set prior to the onset of unacceptable jam rates.
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.
