Patent Publication Number: US-7917049-B2

Title: Variable interference cleaning blade method

Description:
Cross referenced and commonly assigned U.S. application Ser. No. 11/877,770, filed Oct. 24, 2007 and entitled LONG LIFE CLEANING SYSTEM WITH REPLACEMENT BLADES by Bruce E. Thayer et al. now U.S. Pat. No. 7,783,210; and U.S. application Ser. No. 12/021,500, filed Jan. 29, 2008 and entitled DUAL BLADE CLEANING SYSTEM by Bruce E. Thayer et al., now U.S. Pat. No. 7,715,776; U.S. application Ser. No. 12/136,086, filed Aug. 31, 2010 and entitled METHOD FOR ADJUSTING CLEANING BLADE LOAD ON A PHOTORECEPTOR by Bruce E. Thayer et al., now U.S. Pat. No. 7,787,793; U.S. application Ser. No. 12/136,088, filed Jun. 10, 2008 and entitled CLEANING METHOD FOR COMPENSATING FOR ENVIRONMENTAL CONDITIONS AND BLADE AGE IN A CLEANING SUBSYSTEM by Bruce E. Thayer et al., now U.S. Pat. No. 7,817,933; all of which are included in their entirety herein by reference. 
     This disclosure relates to an electrostatographic printing system that employs an imaging device, and more particularly, to cleaning residual toner from a charge retentive surface of the imaging device. 
     Electrostatographic machines including printers and copiers form a latent image on the surface of photosensitive material which is identical with an original image, brings toner-dispersed developer into contact with the surface of the photosensitive material, and sticks toner particles only onto the latent image with electrostatic force to form a copied image on a copy sheet. Thus, a toner image is produced in conformity with the original image. The toner image is then transferred to a substrate and the image affixed thereto to form a permanent record of the image to be produced. Although a preponderance of the toner forming the image is transferred to the substrate during transfer, some toner invariably remains on the charge retentive surface of the photosensitive material, it being held thereto by relatively high electrostatic and/or mechanical forces. Additionally, paper fibers, toner additives, kaolins and other debris have a tendency to be attracted to the charge retentive surface. It is essential for optimal imaging that the toner and debris remaining on the charge retentive surface be cleaned therefrom for quality images to be produced by the machines. 
     “Blade cleaning” is a technique for removing toner and debris from a photoreceptor. In a typical application, a relatively thin elastomeric blade member is supported adjacent to and transversely across the photoreceptor surface with a blade edge that chisels or wipes toner from the surface. Toner accumulating adjacent to the blade is transported away from the blade area by a toner transport arrangement or by gravity. Blade cleaning is advantageous over other cleaning systems due to its low cost, small cleaner unit size, low power requirements, and simplicity. However, conventional blade cleaning systems suffer from short life due to early, random failures. Attempts to identify blade materials that possess better reliability and enable dramatic life improvements have not been successful. Introduction of additional blade lubrication can significantly improve blade reliability and life, but adverse interactions with other xerographic systems frequently occur. The introduction of photoreceptor surface coatings has improved photoreceptor life, but these coatings typically result in far higher blade wear rates. Improvements from the introduction of additional lubrication are typically more than offset by the use of coated photoreceptors. 
     Cleaning blades are typically designed to operate at either a fixed interference or fixed blade load as disclosed in U.S. Pat. No. 5,208,639 which is included herein by reference. Because of blade relaxation and blade edge wear over time, part and assembly tolerance, and cleaning stresses from environmental conditions and toner input, the cleaning blade is initially loaded to a blade load high enough to provide good cleaning at extreme stress conditions for all of the blade&#39;s life. For most of the blade&#39;s life its blade load is higher than required for good cleaning. For some blades the extreme stress conditions that the initial blade load is designed for will never occur. A negative result of the blade load being higher than required for good cleaning is that the blade and charge retentive surface wear more quickly. Overcoated charge retentive surfaces have been developed to reduce the wear rate. However, these overcoats have also increased the wear rate of the blades. 
     Accordingly, there is an unmet need for systems and/or methods that facilitate overcoming the aforementioned deficiencies. 
     In accordance with various aspects described herein, systems and methods are described that facilitate cleaning a charge retentive or photoreceptor surface in a xerographic imaging device using cleaning blades. For example, a cleaning apparatus for a moving photoreceptor surface comprises a cleaning unit with a blade holder that rotates about a pivot point to adjust blade interference to provide the minimum load for high quality cleaning. A stepper motor is used to increase or decrease interference of the blade to the photoreceptor surface. A full width array (FWA) sensor is used to monitor the photoreceptor surface after the cleaner. When toner past the cleaning blade is detected, the stepper motor increases blade interference until the blade load is high enough to eliminate the cleaning failure. Monitoring for cleaning failures can be during printing operation and can be during a non-printing cycle when a developed toner patch is used to evaluate cleaning. Interference is reduced during the non-printing cycle until a cleaning failure occurs at the minimum blade load for cleaning. Operating at the minimum load reduces blade and photoreceptor wear for longer life. Finding the minimum load for inboard and outboard patches aligns the blade to the photoreceptor. 
    
    
     
       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: 
         FIG. 1  is a side view of a cleaning system that enables blade cleaning performance sensing and adjustment of blade to photoreceptor interference; 
         FIG. 2  is a schematic of a single stepper motor system used in the cleaning system of  FIG. 1  to control blade load to the minimum required for cleaning; 
         FIG. 3  is flowchart of the process to determine minimum blade load to clean for a single stepper motor system; 
         FIG. 4  is a perspective view illustrating an alternative two blade cleaning system having a doctor blade arrangement as described herein with a first cleaning blade disposed in the cleaning position; 
         FIG. 5  is a perspective view of the two blade cleaning system of  FIG. 4  having a doctor blade arrangement as described herein with a second cleaning blade disposed in the cleaning position; 
         FIG. 6  is a schematic of a two stepper motor system used in the cleaning system of  FIG. 1  to control blade load to a minimum required for cleaning and to align the blade to the photoreceptor; and 
         FIG. 7  is a flowchart of a process to determine minimum blade load calibration on a photoreceptor with a two stepper motor system with every new blade and after every predetermined number of prints. 
     
    
    
     With reference to  FIG. 1 , a system is illustrated that facilitates replacing a used cleaning blade with a cleaning blade at the end-of-life (EOL) of the used cleaning blade, or at any other desired replacement time while simultaneously adjusting blade interference to provide the minimum load high quality cleaning. The system is illustrated in a first orientation  10  wherein the first cleaning blade is in use, and in a second orientation  11 , wherein the second cleaning blade is in use. The system comprises a cleaner unit  12 , that is in operational contact with a photoreceptor  14 , and houses a blade holder  16 , which in turn has a first blade  18  and a second blade  20  attached thereto. The blade holder  16  pivots about a pivot point  22  to position the first or second blade against the surface of the photoreceptor  14 , which has a direction of rotation indicated by the arrow at the bottom of the photoreceptor  14  (e.g., counterclockwise in this example). The blade, when placed against the surface of the photoreceptor  14 , removes excess waste toner  24 , which is directed toward a toner removal auger  26  that removes the waste toner  24  from the cleaner unit  12 . Waste toner  24  may then be discarded, recycled, etc. Though some examples provided describe a system for cleaning moving photoreceptor surfaces  14 , the cleaning system can also clean other image forming device moving surfaces, including but not limited to moving transfer surfaces such as biased transfer belts, biased transfer rolls, or intermediate transfer belts. 
     The system further comprises a sensor  28  that senses status information related to print quality, toner build-up, blade wear, or any other suitable parameter for determining an appropriate time for switching blades. The sensor can comprise one or more counters  30  that facilitate determining when to change a blade. An actuator  32  performs the blade change, and may be manual (e.g., a knob, lever, cam, or other actuating means that an operator manipulates to effectuate the blade change) or automatic (e.g., a motor, solenoid, etc.) that changes the blade in response to a sensed blade change condition. 
     Thus, the system comprises a compact cleaning blade unit having two or more blades that are positioned so that toner flow is not impeded and so that accumulated toner does not apply pressure to the operating blade. Simple rotation of the blade holder removes a used blade and replaces it with a new blade. The photoreceptor surface can be stationary or moving backwards from normal operation during blade replacement. The sensor  28  detects accumulated blade use in one or more ways. For instance, the counter  30  can measure blade use as a function of a number of prints and/or as a function of photoreceptor cycles. 
     In accordance with the present disclosure and as disclosed in  FIG. 2 , rotation of blade holder  16  through blade positioning mechanism  40 , which could be a shaft or other conventional mechanism, controls the amount of interference for each blade in the assembly. By controlling the amount of rotation, the blade load can be varied. A stepper motor  45  is used to provide rotation of blade holder  16  in defined increments. Full width array (FWA) sensor  60  is positioned after cleaner  12  to provide a detection system for streaks of toner passing under the cleaning blade. The output from the FWA sensor is input to a controller  50 . Controller  50  sends a signal to stepper motor  45  to increase blade interference until feedback from the FWA sensor  60  indicates that the cleaning defect has been eliminated. Because cleaning failures are visible on the surface of photoreceptor  14  well before they are visible on prints, the operator on the machine will be unaware of any cleaning problem and cleaning monitoring need not be continuous. 
     The method or process described hereinabove maintains the cleaning blade load above the minimum load for cleaning. This is useful for preventing cleaning failure for preventing cleaning failures during operation of the machine, but it does not optimize cleaning blade life. To optimize cleaning blade life, the blade load must be kept at the minimum load for cleaning. This will result in the lowest possible wear on the cleaning blade and the photoreceptor while still maintaining good cleaning. If blade interference is increased to increase blade load during a high temperature stress condition, then the blade load will be higher than required for good cleaning when the temperature returns to normal or cold conditions. A procedure is required for reducing cleaning blade load once the stress condition requiring a higher blade load no longer exists. 
     Accordingly, and accordance with another aspect of the present disclosure, a procedure for reducing cleaning blade load once the stress condition requiring a higher blade load no longer exists is disclosed that includes development of a toner patch for cleaning evaluation. The toner patch is not transferred, but enters the cleaner as a high density stress image. As shown in the flow chart of  FIG. 3 , the process of finding the minimum load to clean the photoreceptor is initiated in block  80  and a decision is made in block  81  as to whether the photoreceptor is clean or not. If the FWA sensor  60  detects toner past the cleaning blade, then the blade interference is increased in block  82  and toner is again sensed by the FWA sensor with this procedure continuing in decision block  83  until the minimum load for cleaning the photoreceptor is reached in block  86 . If the FWA sensor does not detect toner past the cleaning blade in block  81 , then the blade interference is decreased in block  84  until the minimum load for cleaning is reached. Since this process generates toner streaks past the cleaning blade, it is best preformed during non-printing operation of the machine. This could be during a special cleaning evaluation cycle or preferably during machine cycle-up, cycle-down or even in inter-document zones. 
     An advantage of the cleaner configuration of  FIG. 2  with a FWA sensor to detect cleaning failures is the capability of adjusting blade interference over time to compensate for blade set that otherwise would result in a loss of blade load due to blade material relaxation under prolonged strain. Similarly, changes in blade material modulus due to environmental changes in humidity and temperature can be compensated for by changing interference. Blade material response to relaxation or environmental performance removes relaxation and environmental considerations as constraints on blade material selection. 
     Another two blade cleaning system is shown in  FIG. 4  where an image forming device is shown generally at  110 . The image forming device  110  can be a copier, such as a xerographic copier, a printer, multifunction device or other device having a photoreceptor  112  for forming an image on a substrate such as for example paper (not shown), having a moving surface  114  which moves in an operational direction shown generally by arrow  115 . 
     The image forming device  110  includes a cleaning system, shown generally at  116 , for cleaning toner particles, residue and other materials from a moving photoreceptor surface  114 . Though some examples provided describe a system for cleaning moving photoreceptor surfaces  114 , the system  116  can also clean other image forming device moving surfaces, including but not limited to moving transfer surfaces such as biased transfer belts, biased transfer rolls, or intermediate transfer belts. 
     The cleaning system  116  can be contained in a removable cartridge housing  117 , if so desired, such as for example part of a print cartridge, also referred to a Xerographic Replaceable Unit (XRU). The XRU can be removed from the image forming device  110  and discarded when its useful life has been depleted. 
     The cleaning system  116  includes a first cleaning blade  120  having a cleaning blade member  122  extending from a blade holder  124  and terminating in an end  129 . The blade, when placed against the surface of the photoreceptor  114 , removes excess waste toner which is directed toward a toner removal auger  190  that removes the waste toner from the cleaner unit  116 . Waste toner may then be discarded, recycled, etc. The cleaning system  116  also includes a second cleaning blade  140  having a cleaning blade member  142  extending from a blade holder  144  and terminating in an end  149 . The cleaning blade members  122 ,  142  can be formed of a compliant material, such as polyurethane, which enable the blade members to bend or deflect when moved into cleaning contact with the moving surface  114 . 
     The cleaning system  116  includes a pair of first links  160  formed of a rigid material, such as metal, plastic, composites or the like. The first links  160  are connected to opposite lateral ends of the cleaning blades  120  and  140  to couple the cleaning blades together for moving one blade member into a cleaning position while simultaneously moving the other blade into a corresponding suspended position. The first links  160  are similar, and thus only one first link is shown in detail for the purposes of clarity. The first links  160  include first pivot connections  162  pivotally connected to the distal portions  134  of the oppositely disposed lateral ends  126  and  128  of the first blade holder  124 . The first links  160  also include second pivot connections  164  pivotally connected to the distal portions  154  of the lateral ends  146  and  148  of the second blade holder  144 . The first links  160  also include third pivot connections  166  pivotally connected to one or more frame members  167 , enabling the first links to rotate about a fixed axis A while preventing non-pivoting displacement of the first links with respect to the frame. The frame  167  can be part of the cartridge  117 , or a support member attached to the image forming device  110 . 
     The cleaning system  116  also includes a pair of second links  170  formed of a rigid material, such as metal, plastic, composites or the like. The second links  170  are connected to opposite lateral ends of the cleaning blades  120  and  140  to also couple the cleaning blade members together. The second links  170  are similar, and thus only one second link is shown in detail for the purposes of clarity. The second links  170  include first pivot connections  172  pivotally connected to the proximate portions  132  of the oppositely disposed lateral ends  126  and  128  of the second blade holder  124 . The second links  170  also include second pivot connection  174  pivotally connected to the proximate portions  152  of the lateral ends  146  and  148  of the second blade holder  144 . The second links  170  also include third pivot connections  176  pivotally connected to one or more of the frame members  167 , enabling the second links to rotate about a fixed axis B. 
     The first and second link pivot connections  162 ,  164 ,  166 ,  172 ,  174 , and  176  can be formed by fasteners, such as rivets, bolts or the like extending from the blade holders  124 ,  144  or frame  167 , and through apertures in the first and second links  160 ,  170 , or in other manners which enable relative rotation at the connections. The pivot connections  162 ,  164  and  166  are disposed in a triangular arrangement on the first links  160 , and the pivot connections  172 ,  174  and  176  are disposed in a triangular arrangement on the second links  170 . The first and second links  160 ,  170  can be V-shaped, each having 2 legs extending from the third pivot connections  166 ,  176  with the first pivot connections  162 ,  172  and second pivot connections  164 ,  174  disposed at the ends thereof, as shown in  FIGS. 4 and 5 . Such an arrangement can enable the links to be located close to each other without interfering in their movement. Other examples of the links  160 ,  170  can have triangular shapes with the pivot connections disposed at the vertices thereof. Other examples of the links can have other shapes. 
     An actuator  194 , as shown in  FIG. 5 , can be connected to one of the first links  160  to rotate it about the third pivot connection  166 . The actuator  194  can be a solenoid, or stepper motor, or some other actuator capable of rotating the first link  160  at connection  166 . The actuator  194  can be disposed at the third pivot connection  166 , or it can be disposed in another location and connected to the first link  160 , such as by gears, arms, etc. so as to provide rotational movement to the first link  160 . Other actuator arrangements capable of rotating the first and second links  160  and  170  about the third pivot connections,  166  and  176  respectively, are contemplated including, but not limited to using an actuator, shown at  195 , connected to one of the second links  170  to rotate it about the third pivot connection  176 , or two actuators  194  connected to each of the first links  160  or two actuators  195  connected to each of the second links  170  for rotating them about the third pivot connections  166  and  176 , respectively. The first or second link driven by the actuator  194  or  195 , for rotation can be referred to as the drive link, whereas the undriven link can be referred to as the follower link. 
     A small amount of clearance is intentionally introduced into pivot connections  166  and  176  of blade holders  124  and  144 , respectively, in order to be able to vary the interference on one end of the blade slightly from the interference on the other end of the blade. By using this variation and a stepper motor on each end of the blade, independent adjustments of each blade end interference and thus blade load can be obtained. Both inboard and outboard cleaning evaluation toner patches are developed. The stepper motors independently adjust inboard and outboard blade interference until both toner patches are cleaned with the minimum blade load. This procedure aligns the cleaning blade to the photoreceptor based on cleaning performance. The alignment is independent of variability in parts and assembly. 
     A schematic of the cleaning performance control system for  FIGS. 4 and 5  is shown in  FIG. 6  that includes two stepper motors  45  and  46  operatively connected in this example to pivot connection  166  to thereby manipulate cleaning blade  122 . It should be understood that pivot connection  176  is operatively connected to stepper motors on opposite ends of blade  142  as well for manipulating the second blade. As photoreceptor  112  rotates in the direction of the arrow, toner patches on either side of the photoreceptor are sensed by FWA  60 . Rotation of blade holder  124  through blade positioning mechanism  40 , which could be a shaft or other conventional mechanism, controls the amount of interference for each blade in the assembly. By controlling the amount of rotation, the blade load can be varied. Stepper motors  45  and  46  are used to provide rotation of blade holder  124  in defined increments. Full width array (FWA) sensor  60  is positioned after cleaner  116  to provide a detection system for streaks of toner passing under the cleaning blade. The output from the FWA sensor is input to a controller  50 . Controller  50  sends a signal to stepper motors  45  and  46  which controls outboard blade positioning mechanism  40  and inboard blade positioning  42  to increase blade interference until feedback from the FWA sensor  60  indicates that the cleaning defect has been eliminated. Because cleaning failures are visible on the surface of photoreceptor  112  well before they are visible on prints, the operator on the machine will be unaware of any cleaning problem and cleaning monitoring need not be continuous. 
       FIG. 7  is a flow chart of the process for performing blade load calibration with new blades and after every predetermined number of prints. In block  200  the process is initiated and in block  201  a cleaning stripe across the full width of the photoreceptor  14  is developed. The blade is incrementally retracted to reduce blade load on the surface of the photoreceptor until defects are recognized across the full width of the blade in block  202 . Both ends of the blade are incremented toward the surface of the photoreceptor in block  203  and a decision is made in block  204  as to whether or not the incrementing is at its limit. If the answer is YES, as shown in block  208 , the blade is replaced. If the answer is NO, linear interpolation is used in block  205  between the known positions of the blade ends to determine location of defects. The defects are recorded in a location register in block  206  and the question is asked in block  207  as to whether there are defects. If the answer is YES, the process is repeated in blocks  203 - 207 . If the answer is NO, a determination is made in block  209  as to the optimum position for long blade life based on: minimizing interference at the higher interference end; minimizing the sum of differences between blade position and failures positions; and constraining positions to those without failure. 
     Afterwards, the blade is moved in block  210  to its optimum position. Cleaning performance is monitored in block  211  for defects. A decision is made in block  212  as to whether there are any defects. If the answer is NO, a decision is made in block  216  as to whether the last adjustment was greater than a predetermined number of prints ago. If the answer in block  216  is YES, both ends of the blade are incremented away from the photoreceptor surface to reduce blade load until one or more defects occur and the inquiry is made as to whether there are any defects in block  212 . If the answer in block  216  is NO, cleaning performance is monitored for defects in block  211  with the process proceeding then to block  212  with the decision as to whether or not there are any defects. If the answer is YES in block  212 , a decision is made as to whether or not the incrementing limit has been reached in block  213 . If that answer is YES, the blade is replaced as shown in block  218 . However, if the answer is NO, linear interpolation is used between the known positions of the blade ends to determine the location of defects in block  214  and the defect location register is updated in block  215  and the process is repeated starting with block  209 . 
     It should be understood that while the variable interference cleaning blade system hereinabove has been shown in a multi-blade system, it is adaptable and equally effective in a single blade cleaning system. 
     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.