Abstract:
A xerographic printer or copier includes a replaceable cartridge having a cleaning blade and carrier particle pickoff member associated with a rotating charge receptor. As the cartridge is being used, carrier particles removed from the photoreceptor by the cleaning blade are magnetically retained on the pickoff member, where the remain for the balance of the lifetime of the cartridge. When a useable lifetime of the cartridge is spent, the carrier particles are removed from the pickoff blade.

Description:
TECHNICAL FIELD 
   The present disclosure relates to xerographic printing, and in particular to the removal of carrier particles, from a two-component developer material, from the surface of a photoreceptor in a xerographic cleaning step. 
   BACKGROUND 
   In an electrophotographic printing machine, a photoconductive member, such as a photoreceptor, is charged to a substantially uniform potential to sensitize the surface thereof. The charged portion of the photoreceptor is thereafter selectively exposed. Exposure of the charged photoreceptor dissipates the charge thereon in the irradiated areas. This records an electrostatic latent image on the photoreceptor corresponding to the informational areas contained within the original document being reproduced. After the electrostatic latent image is recorded on the photoreceptor it is “developed.” The development process deposits toner in the same pattern as the latent image on the photoreceptor. This developed toner is subsequently transferred to a print sheet. The sheet is then heated to permanently affix the toner image thereto in image configuration. 
   The electrostatically attractable developing material commonly used in developing systems comprises a pigmented resinous powder referred to here as a “toner” and a “carrier” of larger granular carrier particles formed with iron, steel, or ferrite cores coated with a material removed in the triboelectric series from the toner, so that a triboelectric charge is generated between the toner powder and the granular carrier. The toner is attracted to the electrostatic latent image from carrier bristles to produce a visible powder image on an insulating surface of the photoreceptor. 
   In a practical application, however, some carrier particles will adhere to the photoreceptor after an area of the photoreceptor leaves the development zone. These adhering carrier particles prevent intimate contact between the support surface (e.g., a sheet of paper) and the toner particles, and they may affect the quality of the copy produced. In addition, because such adhering carrier particles are hard, they may abrade the surface of the photoreceptor if not removed prior to reaching the cleaning zone. Consequently, it is desirable that all such carrier particles be removed from the photoreceptor with each cycle of the photoreceptor. 
   Many designs of xerographic printers and copiers use what will here be called “customer-replaceable units” or CRUs, or more generally “cartridges.” Typically a CRU will include a photoreceptor and ancillary hardware, such as a corotron or equivalent charge device and a cleaning station. The CRU is designed to be easily removed from the larger machine and replaced with an effectively new CRU. Used CRU&#39;s can in various ways be remanufactured, such as by cleaning the CRU, replacing spent parts such as the photoreceptor, and refilling the CRU with a new supply of marking material. The present disclosure relates to a carrier particle pickoff device suitable for inclusion in a CRU. 
   PRIOR ART 
   U.S. Pat. No. 4,868,607 discloses a particle pickoff device in which a particle catch is disposed in close proximity to a photoreceptor belt, to draw off carrier particles. The drawn carrier particles are accumulated in a container. 
   U.S. Pat. No. 5,315,357 discloses an apparatus for removing single component magnetic toner, as opposed to carrier, from a photoreceptor in a xerographic printer. 
   The Xerox® 1090® copier includes a pickoff device which will be described below with reference to  FIG. 4 . 
   SUMMARY 
   According to one aspect, there is provided a cartridge for operating within a xerographic printing apparatus, comprising a blade for engaging a rotatable charge receptor, and a pickoff member, having magnetic properties associated therewith, disposed near the blade. The pickoff member magnetically retains carrier particles thereon for a lifetime of the cartridge. 
   According to another aspect, there is provided a method of operating at least one xerographic printing apparatus. A cartridge is removed from a xerographic printing apparatus, the cartridge including a blade for engaging a rotatable charge receptor and a pickoff member disposed near the blade, the pickoff member magnetically retaining carrier particles thereon. Retained carrier particles are removed from the pickoff member, using a wiper which is not part of the cartridge. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a simplified elevational view showing elements of an electrostatographic or xerographic printing apparatus. 
       FIG. 2  is an elevational view of a cleaning station which is part of a CRU or cartridge. 
       FIG. 3  is a simple flow-chart showing some steps in a CRU remanufacturing process. 
       FIG. 4  is a simplified elevational view of a pickoff device used in the prior art. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a simplified elevational view showing relevant elements of an electrostatographic or xerographic printing apparatus, such as a printer, copier, or multifunction device generally indicated as  99 . Certain elements of the apparatus are disposed within a CRU, or cartridge, generally shown as  100 . As will be described in detail below, those parts of the overall machine  99  which require replacement or periodic service are typically placed within CRU  100 , while longer-lasting parts are elsewhere in the machine. 
   As is well known, an electrostatic latent image is created, by means not shown, on a surface of a rotatable charge receptor or photoreceptor  10 . The latent image is developed by applying thereto a supply of toner particles, such as with developer roll  12 , which may be of any of various designs, such as including a magnetic brush roll or donor roll, as is familiar in the art. The toner particles adhere to the appropriately-charged areas of the latent image. The surface of photoreceptor  10  then moves, as shown by the arrow, to a transfer zone created by a transfer-detack assembly generally indicated as  14 . Simultaneously, a print sheet on which the desired image is to be printed is drawn from supply stack  16  and conveyed to the transfer zone  14  as well. At the transfer zone  14 , the print sheet is brought into contact or at least proximity with a surface of photoreceptor  10 , which at this point is carrying toner particles thereon. A corotron or other charge source at transfer zone  14  causes the toner on photoreceptor  10  to be electrically transferred to the print sheet. The print sheet is then sent to subsequent stations, as is familiar in the art, such as a fuser and finishing devices (not shown). 
   Following transfer of most of the toner particles to the print sheet in the transfer zone, any residual toner particles remaining on the surface of photoreceptor  10  are removed at a cleaning station.  FIG. 2  is an elevational view showing a detail of a cleaning station, which in the embodiment is part of CRU  100 . As can be seen in the Figure, a cleaning blade  22  which is pressed against the surface of photoreceptor  10  scrapes the residual toner off the surface. The toner which is thus removed falls downward into a hopper  24  for accumulating the toner. A flexible flap seal  26 , extending the length of the photoreceptor  10 , prevents loose toner from escaping the hopper. An auger  28 , with an anti-bridging device  30 , is used to remove waste toner (as opposed to carrier particles) from the hopper  24 . 
   Further as shown in  FIG. 2 , there is associated with cleaning blade  22  a permanent magnet  40  and a pickoff blade  42 . The magnet  40  and blade  42  extend substantially the length of the cleaning blade  22  (going into the page, in the view of  FIG. 2 ). The tip of pickoff blade  42  is disposed between 0.5 mm and 2.0 mm from the photoreceptor  10 . The pickoff blade  42  should exhibit some ferro-magnetic properties, so that magnetic flux passes effectively therethrough. The interaction of the magnet  40  and pickoff blade  42  results in a significant magnetic flux through the tip of the pickoff blade  42 . The magnetic flux emanating from the pickoff blade  42  attracts carrier particles, before or as they are stopped by cleaning blade  22  on the moving surface of photoreceptor  10 . By removing carrier particles from the photoreceptor surface in the cleaning blade area, the pickoff blade  42  prevents scratching of the surface of photoreceptor  10  by stray carrier particles. The cleaning blade  22 , of course, also removes residual toner particles from the photoreceptor  10 , but that action is largely irrelevant to the behavior of the carrier particles. 
   As mentioned above, certain hardware elements of the overall machine  99  can be isolated into a CRU (customer-replaceable unit), or more generally “cartridge,”  100 , which is readily removable (and thus replaceable) relative to the whole printer. Typically the CRU  100  includes parts of the printer hardware that wear out, become dirty, or are consumed as the machine is used. In the illustrated embodiment, such parts include the photoreceptor  10 , as well as various seals and bushings (not shown). Depending on an overall machine design, the CRU  100  can include a supply of marking material in a container  50 , as shown in  FIG. 1 ; in other designs the marking material supply is in a second CRU which is separate from a CRU holding the photoreceptor  10 . In any case, a typical “lifetime” of a CRU is in the tens of thousands of prints output by the machine  99 ; as used herein, the lifetime of a CRU or cartridge is defined as an amount (which can be expressed, for instance, as time, prints made, or consumable material used) of satisfactory use of the cartridge before the cartridge needs to be replaced with a new or otherwise remanufactured or refurbished cartridge. When a cartridge is remanufactured or refurbished, it becomes for practical purposes “new” and gets a new lifetime. The lifetime of a cartridge is contrasted with the lifetime of the overall machine  99 , which is intended to be many multiples that of the cartridge. 
   Returning to  FIG. 2 , as carrier particles are attracted toward the pickoff blade  42 , the carrier particles remain on the pickoff blade for the remaining lifetime of the CRU  100 . In practical terms, the particles remain on the pickoff blade  42  when the whole CRU  100  is removed from machine  99 . Only after the CRU  100  is removed from machine  99 , thus ending the particular lifetime of the CRU  100 , and a refurbishing process is carried out on the CRU  100  are the particles removed from the pickoff blade  42 . Of course, at the end of a lifetime the whole CRU  100  may simply be discarded, and the removal of carrier particles therefrom rendered unnecessary. 
     FIG. 3  is a simple flow-chart showing some steps in a CRU remanufacturing process. At step  300  a CRU  100 , deemed to be at the end of its lifetime by one or more of various criteria such as time, prints made, detection of faults, etc., is removed from a machine  99 . At step  302  the removed CRU  100  is opened and generally cleaned, the cleaning including removing carrier particles which are magnetically attached to pickoff blade  42 . The removal of carrier particles from pickoff blade  42  can be carried out by generally-known means, such as the use of brushes, blades, and/or vacuum devices (generically called a “wiper”), and can be part of a general cleaning operation on the whole of CRU  100 . The brushes, blades, and/or vacuum devices for removing the carrier particles from pickoff blade  42  are, in this embodiment, not part of the CRU  100  itself. Other common steps used in the remanufacturing of cartridges include replacement of photoreceptor  10  (step  304 ), and refilling of the developer supply  50  (step  306 ). Once the CRU  100  is re-assembled and tested for proper operation, the CRU  100  is ready for re-installation in the same or another machine  99  (step  308 ), and a new lifetime of the CRU is deemed to begin. 
   Although in the illustrated embodiment the carrier particles are retained on a pickoff blade and is disposed a predetermined distance from the cleaning blade and from the photoreceptor, in other embodiments the pickoff blade or member could, for instance, be directly in contact with the cleaning blade. Alternately, the pickoff member could be mounted from an inner wall of the CRU. 
     FIG. 4  is a simplified elevational view of a pickoff device used in the prior art, in this case the Xerox® 1090® series of copiers and printers. In  FIG. 4 , like reference elements relate to corresponding structures in the above-described Figures. There is present a permanent magnet  40  and a pickoff blade  42 , but the assembly thereof is surrounded by a rotatable sleeve  70 , a portion of which is disposed near the portion of photoreceptor  10  desired to have carrier particles removed therefrom. Thus, carrier particles, indicated as C, drawn off of photoreceptor  10  do not contact pickoff blade  42  but rather the sleeve  70 . As sleeve  70  rotates, the carrier particles remain thereon, as shown, until the magnet  40  ceases to have sufficient influence to hold the carrier particles on the sleeve  70 , as is evident on the right-hand side of the sleeve  70  in the Figure. The particles which thus fall off of sleeve  70  are then directed (either directly, or indirectly, such as through augers and pipes, not shown) to a separate collection bottle  72 , which, in this particular embodiment, is not part of a CRU including photoreceptor  10  or pickoff blade  42 . 
   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.