Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to commonly-assigned copending U.S. patent application Ser. No. __/___,___ (Attorney Docket No. 96607/NAB), filed herewith, entitled DISENGAGING AN IMAGING MEMBER FROM A PHOTOCONDUCTOR, by Pitas et al.; the disclosure of which is incorporated herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to electrophotographic printing in general, and in particular to a shield for a photoconductor. 
       BACKGROUND OF THE INVENTION 
       [0003]    An electrophotographic printer uses sensitive components that must be routinely serviced by either dedicated service personnel or by the end user. Many of these components are easily damaged unless care is exercised during replacement. In some instances, it is considered imprudent to depend upon an individual exercising care as a step in carrying out a critical operation. This is especially important when the risk of error is high and the cost and machine down-time associated with error is great. 
         [0004]    A primary component requiring frequent replacement within an electrophotographic print engine is the photoreceptive member. The function of the photoreceptive member is to provide a means of developing an image and transferring that image to paper. The photoreceptive member is coated with a photosensitive material which is essential to operation of the electrographic printer. The photosensitive material is easily scratched and can be damaged by exposure to ambient light if handled incorrectly. 
         [0005]    In addition, components that normally come in contact with the photoreceptor may themselves become damaged by or do damage to the photoreceptor if they remain in contact for a prolonged period of time. This type of damage creates unacceptable image quality defects in the transferred image. Some prior art designs incorporate black paper as a means of separation of imaging components from the photoreceptive member. The black paper is wrapped tightly around the photoreceptor during replacement of the photoreceptor in the electrophotographic printer. A disadvantage of black paper is that the components are loaded against the paper such that when the paper is removed, an abrasive action occurs between the imaging member and photoreceptor. Rollers and cleaning blades may also become mechanically deformed, impairing proper function. 
         [0006]    A means to decouple components from the photoreceptor would be desirable. 
       SUMMARY OF THE INVENTION 
       [0007]    Briefly, according to one aspect of the present invention an apparatus for engaging and disengaging an imaging member from a photoconductor includes a shield enclosing the photoconductor. A detent on the shield to maintains a space between the imaging member and the photoconductor. Removing the shield allows the imaging member to move into contact with the photoconductor when the photoconductor and shield are inserted into an electrophotographic apparatus. 
         [0008]    The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic cross-section of a replacement cartridge. 
           [0010]      FIG. 2  is a cross-section of a replacement cartridge in an electrophotographic printer with protective guards according to the present invention. 
           [0011]      FIG. 3  is a replacement cartridge with protective guards removed. 
           [0012]      FIG. 4  is a detail of a charging device separated from a photoreceptor within a replacement cartridge. 
           [0013]      FIG. 5  is a detail of a charging device engaged to a photoreceptor within a replacement cartridge. 
           [0014]      FIG. 6  is a detail of a cleaning device separated from a photoreceptor within a replacement cartridge. 
           [0015]      FIG. 7  is a detail of a cleaning device engaged to a photoreceptor within a replacement cartridge. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The present invention will be directed in particular to elements forming part of, or in cooperation more directly with the apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. 
         [0017]    An electrophotographic printer includes components necessary to accomplish the task of printing an image on paper. Various sub-assemblies of the printer perform specific functions. 
         [0018]    An imaging module consists of components to enable printing of a single color image. Multiple imaging modules may be assembled to enable printing of multiple color images.  FIG. 1  shows details of a typical imaging module  31 , which may be assembled with other imaging modules to enable color printing. 
         [0019]    Within the imaging module  31  are various subsystems referred to collectively as imaging members but specifically referred to according to their function. Charging subsystem  210  uniformly electrostatically charges photoreceptor  206  of photoreceptive member  111 , shown in the form of an imaging cylinder. Charging subsystem  210  may include a grid  213  having a selected voltage, or may be in the form of a charging roller with conductive properties. 
         [0020]    Additional imaging members provided for control may be assembled around the various process elements of the respective printing modules. For example, meter  211  measures the uniform electrostatic charge provided by charging subsystem  210 , and meter  212  measures the post-exposure surface potential within a patch area of a latent image formed from time to time in a non-image area on photoreceptor  206 . 
         [0021]    Image writer  220  is used to expose photoreceptor  206  and may be a light emitting diode (LED) array or other similar mechanisms or laser. Toning unit  225 , comprising elements  226  and  227 , is used to develop the latent image created by image writer  220  on photoreceptor  206 . Cleaning unit  230  removes residual toner from photoreceptor  206  after transfer of the image to a secondary receiver. Other meters and components may be included. 
         [0022]    Within the imaging module  31 , periodic replacement of critical components is necessary to ensure proper function. It may be desirable to cluster multiple components to enable simultaneous replacement. Referring to  FIG. 2 , a replacement cartridge  200  within imaging module  31  is created consisting of a photoreceptive member  111 , and additional imaging members such as a cleaning unit  230 , and charging subsystem  210 . These components are assembled into a cartridge and held in place with a plastic housing  233 . Further, protective guards  231   a  and  231   b  are applied to the module, which serves to prevent damage to the photoreceptor  206  of the photoreceptive member  111 . The replacement cartridge slides into the electrophotographic printer with guides  232   a  and  232   b.  Guides  232   a  and  232   b  are attached to the printer and help mount and align the replacement cartridge in the proper position. 
         [0023]    Because of the proximity of various imaging members that interface with imaging module  31  and with replacement cartridge  200 , it is necessary to have large areas of the photoreceptive member open during use. During insertion into the print engine, these open, unprotected areas could be damaged either mechanically or by light exposure. Therefore it is necessary to protect the photoreceptive member  111  from damage, either from extraneous light, fingerprints, or mechanical scrapes. The protective guards  231   a  and  231   b,  also referred to as a removable shield, slide into grooves within the replacement cartridge housing. These removable shields  231   a  and  231   b  stay in place when the cartridge is installed in the printer, and are removed by sliding the shields out of the housing to the front of the equipment after the replacement cartridge  200  is in place in the printer. 
         [0024]    Referring now to  FIG. 3  a replacement cartridge with shields  231   a  and  231   b  removed is shown. Some components that come in contact with the photoreceptor can cause damage to or be damaged by the photoreceptor  206 . Attached to the protective guards  231   a  and  231   b  of imaging module  31  are actuators which push the charging subsystem  210  away from the photoreceptor  206  such that a gap is created.  FIG. 4  shows a detail of a charging subsystem  210  separated from a photoreceptor  206 , wherein separation is maintained by an actuation feature  241  mounted on protective guard  231   b.  Spring  242  provides actuation tension toward the photoreceptor. 
         [0025]    Similar features may be used to actuate the cleaning unit  230 , or other imaging members as required by the specific design. Referring again to  FIG. 3 , the imaging member remains clear of the photoreceptive member  111  until the protective guards  231   a  and  231   b  are removed from the unit. Because the guards are in place during shipment of replacement cartridges, the shield actuator prevents damage during long term storage. Additionally, if the particular electrophotographic printer design requires that the components in the machine be decoupled during periods of non-use the guards may be reinstalled to decouple the imaging member. 
         [0026]    Referring now to  FIG. 5 , a detail of a charging subsystem  210  engaged to a photoreceptor  206 , is shown with protective guard  231   b  removed. Spring  242  ensures contact of charging subsystem  210  to the photoreceptor  206 .  FIG. 6  shows a detail of a cleaning unit  230  separated from a photoreceptor  206 , wherein separation is maintained by an actuation feature  243  mounted on protective guard  231   a.  Spring  244  provides actuation tension toward the photoreceptor. 
         [0027]    Referring now to  FIG. 7  a detail of a cleaning unit  230  engaged to a photoreceptor  206  is shown, with protective guard  231   a  removed. Spring  244  ensures contact of cleaning unit  230  to the photoreceptor  206 . 
         [0028]    It should be noted that various means of providing actuation force toward the photoreceptor may be used, and that the critical essence of the invention is the use of an actuation feature on said protective guards which enables the retraction and actuation of various imaging members through presence of said protective guards. In addition to the actuation of imaging members within the electrophotographic cartridge, similar means may be used to actuate imaging members such as toning unit  225  and image writer  220  from the photoreceptor  206 . 
         [0029]    Although the devices discussed require physical contact for proper performance, elements such as image writer  220 , charger subsystem  210  if comprised of a corona charger and electrometers require a critical separation distance for proper function. For this consideration the removal of guards enables the actuation spring to pull the imaging member to a mechanical stop rather than the photoreceptor  206  acting as the mechanical stop. 
         [0030]    In addition to the considerations discussed above a characteristic of the actuation feature is that when the guards are reinserted into the replacement cartridge, the various imaging members become separated from the photoconductor, allowing the removal of the replacement cartridge, or if separation only is needed to act as a countermeasure for a short term phenomena, can serve to do so within the machine. 
         [0031]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention. 
       PARTS LIST 
       [0000]    
       
           31  imaging module 
           111  photoreceptive member 
           200  replacement cartridge 
           206  photoreceptor 
           210  charging subsystem 
           211  meter 
           212  meter 
           213  grid 
           220  image writer 
           225  toning unit 
           226  element 
           227  element 
           230  cleaning unit 
           231   a  protective guard (removable shield) 
           231   b  protective guard (removable shield) 
           232   a  guide 
           232   b  guide 
           233  plastic housing 
           241  actuation feature 
           242  spring 
           243  actuation feature 
           244  spring

Technology Category: g